I have frequent episodes of sleep paralysis...when I sleep on my back, I get into these recursive dreams where I believe I'm awake, am laying there, and can't move...I "wake up" only to find I'm stuck again. You actually semi-hallucinate...I've held conversations with my wife in this state she disclaims knowledge of. It can go a half a dozen times in a row, until I can "break out" of it and actually wake up. Once awake, if I turn on my side, I'm usually good at that point.
Knowing what it is makes it a lot more tolerable...the first few times it was distinctly horrifying. I was hearing people break down the door, ie. home invaders, and I was frozen, unable to move. Now, even in the dream state, I know what's going on so it isn't quite as disturbing.