Anyone has ever experienced them?
Yes, I've had them happen for about ten to fifteen years now. Here's a little info on it from
an article at the Standford website.
From my understanding of it there are several "experiences" a person can have. Some just get your typical can't move (me for instance), others get the pressure on the chest, and some get the feeling that there is something in the room with them. I believe there may be more, but that's all I can remember off hand. It's been a while since I researched this. Some of the causes of it happening are exhaustion and stress.
I don't recall the technical terms (maybe they're in the article), but your brain releases a chemical throughout your body that temporarily paralyzes you while your sleeping, in order to "protect" you from accidental harm. The problem is your mind wakes up prior to the dispersion of this chemical. It sucks and can be scary if you don't know what it is, or how to get rid of it.
There are several ways to remove the paralysis. Attempting to make small movements, like fingers and toes helps shake the effects. If you have a spouse, or someone who sleeps beside you, making gutteral noises works too. I'm able to make weird noises that alerts my wife, who promptly shakes me. This works great, the only problem is if I'm talking in my sleep she tends to wake me up, thinking I'm having another episode.
It is terrifying the first couple of times it happens.
Yes, it is. Some years back when I had a third shift job I started experiencing this every single day and it always happened within about twenty minutes of going to bed. For a while there I dreaded going to bed, as I knew it was going to happen.
Simply put, once you learn what it is your experiencing and what causes it, it tends not to happen as often. And when it does, it isn't as much of a problem due to your knowledge of what your experiencing. One thing I also suggest, is attempt to go back to sleep when it happens. It's hard to do, since your "paralyzed", but I've found if I can relax and try to go back to sleep, I'll often jump start a lucid dream. Some of my best lucid dreams have come about from this. The problem is it's hard to relax when your paralyzed.
Edit: Google [google]sleep paralysis[/google] and do some research on it. There's tons of information about it.