I play mostly on Warlord and Noble, not quite ready for more just yet.
Make sure you are playing BTS.
I recommend playing on at least Noble for now, and look to improve your game. Once you get a few basics down then Noble really becomes quite easy and you can start to look at moving up difficulty.
The Strategy & Tips forum is the place to get help and improve your game. It can be found here:
https://forums.civfanatics.com/forums/civ4-strategy-articles.156/
I've noticed some sort of annoying pattern. Mostly on Noble. I don't play Custom games, I play "Play Now" usually with Fractal or Tectonics on Huge with Marathon. Like clockwork, one of my neighbors always DoWs me no matter what; no matter how friendly before, no matter what Trade is like, no matter any factor they always DoW. Then, not long after, there's always a war where the majority of the known Civs around me DoW at the same time. This has happened through every playthrough no matter how I play. Though typically, it doesn't happen until I have 3 to 4 cities. Not sooner. My question is, is this basically hardcoded?
When I do play on Noble, which is only for HOF or GOTM games that are on that level (I normally play IMM/Deity), I find the AI quite passive. I think your issue boils down to two key things - diplomacy and knowing the AI. Ignoring diplomacy or not understand the impacts of relations on certain actions, as well as ways to improve your relations, is eventually going to run you into problems. Likewise, not understanding Leader personalities. Leaders in general are a bit more passive the lower the level, but they can still plot regardless.
So,
1) Take actions to start the process of boosting relations with AIs early on. Open borders, trading resources, trades techs, giving in to reasonable demands/requests, religion/no religion, etc.. Speaking of religion, first you should ignore going for early religions - let AIs do that as the tech path is not optimal. Focus should be a worker techs. Be judicious about adopting a religion, or not adopting one. You can certainly choose to remain neutral on religion which will keep you from diplo malus with other factions. OR you can choose to join a religious bloc and use that to determine wars, build relations with that bloc, or maybe keep you safer longer.
2) Start to learn how different Leaders can be. Who are the nice guys and how are the ones that love to fight. There's actually quite a variety of leader personalities. There are some "warmongers", meaning leaders that are more inclined for war like JC and Mehmed. However, there are a few leaders that are deemed true psychos like Shaka, Monty, Alexander, Napoleon and Genghis. These psychos are coded for high war probs, and will very likely declare on you are someone quite early even at Pleased. (No AI will plot at Friendly, although one single AI can be bribed at Friendly, and she is our lovely Empress Catherine). Furthermore, there are quite a few AIs, including those mentioned, that can plot at "Pleased", or have a higher chance at "backstab". Then you have another bunch that will never plot at "Pleased" like Gandhi, or otherwise are more pacifist. Interestingly, Mansa Musa has a more pacifist personality, and low war prob, but actually can plot at Pleased - though it is quite rare. Conversely, you have a warmonger like Boudicca, who does enjoy a battle, but actually will be good ally at Pleased and never plot against you.
(Note: There is chance that even though AI is at Pleased with you, they may have started plotting prior to hitting Pleased status, so still a chance they might actually DOW you.)
So look to boost relations with Leaders as quick as you can and be careful of things that might piss off an AI. Note "Worst Enemies" as you might have to choose a side - again, think religious blocks and the fact that some Leaders are more inclined to dislike other Leaders based on peace-weights. BUG or BAT mod really helps as well with this information, including a red fist on the scoreboard next to leaders that are plotting.
Anyway, below is an article from the Strategy & Tips Article subforum, that converted leader code into a user friendly guide to each:
https://forums.civfanatics.com/threads/civ-illustrated-1-know-your-enemy.478563/
Lastly, relative power can affect a Leader's plans to attack you. While you don't want to overbuild units - it is expensive - you may want to at least keep a few advance units around. But also make sure you learn the power of slavery and food, so that you can be ready to whip out an army when either you are ready to attack or need to defend yourself.
Unrelated, but on Noble and below, am I ok to leave workers automated? I know it won't get me the most out of them nor the most efficient progress, but micromanaging workers is 1. boring to me (since I am so bad at the game right now that it's hard to divvy up my attention) and 2. I know so little about what's what that I wouldn't even know the right time to place the right thing where for what.
Very simple here: Workers are the most important unit in the game! This is without argument. Automating workers and likewise ignoring good worker management will simply not allow you to improve your game. Furthermore, Civ is very much about the "snowball effect". What you do in the first 50 turns greatly impacts your success/failure the rest of the game, and proper worker management is a BIG part of that.
Once you do learn the strategic importance of managing workers early, then I think you will find the process more enjoyable. You can always start automating worker later game when you grow big and things are in fine shape. But you must improve the right things early and also utilize chops. Automated worker scripting in IV is horrible anyway, so it will not lead you to success.
Keep in mind these things in the process:
1) FOOD is king in this game - it is always your #1 priority first thing. Improve those food specials
2) Worker is most important unit. The sexy Granary is the most important building -hands down
3) Slavery turns food into hammers - it is by far the mos powerful civic in the game. Learning how to use it effectively = WIN
4) Forest chops are free hammers
5) Don't build too many roads early. Main purpose of roads early is to connect trade routes to cities and neighbors (important: this is more commerce) or to hook up resources. Note that rivers can connect resources too. So don't waste turns building useless roads. All worker actions are hugely important early game. (note: automated workers love to build useless roads. I mean they really love it. They will even build roads before improving an important tile)
6) Focus on applicable worker techs first..and Bronze Working.
I typically end up either dead because I tried to keep pace with technology so I neglected a strong enough army to at least defend myself, or I end up with a decent enough sized early army (to fend off the clockwork DoWs and maybe steal a city or two in the process) but well behind on technology.
Well, all this simply goes back to some of the things discussed already and the simple fact of your experience/rustiness with the game. I suspect you never had that much experience when you played before anyway. So time to learn. Go to Strategy & Tips as mentioned. This game and how good you want to become is up to you, but the tools and friendly folks are here for you.
I HIGHLY recommend playing standard settings and maps. Normal speed and standard map size make for more than a satisfying game. You are playing Huge/Marathon games and not learning, leading to long frustrating games of failure. Learn the basics on Normal for now. Get a feel it for and see how satisfying it can be. Normal allows you to play more games and get more experience, instead of days slogging through only a short part of a Marathon game and getting nowhere anyway. Plus, more folks play Normal and there is just a lot of differences in some of the strategies and overall feel of the speeds. While there are still some that do play mainly Marathon here and there, I tend to find that a lot of new players come on here thinking Bigger is Better, but only get frustrated quickly and quit the game or get burned out. Normal games are big.