Do the Dutch typically attack without warning?

So this is a long story. I am playing as Denmark on a Huge map on King. I went to war with Indonesia and after I took their capital they offered me at he city on the other side of their now-capital, so I took it. My intention was to build a force on each side and attack from both sides.

As I am building this force, the Dutch, who I had a mere 3 tile border with and recently "There have been no major incidents to shape your relationship," attacked me out of the blue. I fended off the attack and eventually bribed them to distract Indonesia, allowing me to swoop in and eliminate the Indonesians.

Does William usually attack with little or no warning?

I think any Civ can attack without warning if the situation is right. Your relations with them and their character personality might increase or lessen the chances but that`s all.

^^What Socratatus said.

In fact--I did it to the AI last night. I was friends with Venice the entire game, but in the Modern Age I declined to renew our declaration of friendship. You see--Venice was a wonder whore and kept buliding more and more wonders.

So I thought to myself: "Self, do you want the friendship or attack and grab all those wonders?"

You can guess which I chose

Indeed. Dutch usually attack and known to.