SLEEP ON YOUR SIDE.
I kept getting sleep paralysis when I used to sleep on my back. It is most likely going to happen if you sleep on your back. It can still happen on your side, the effects are just no where near as terrifying.
I have only had it once or twice since changing sleeping positions.
I hallucinate when I do have it. So I have been attacked by terrible things. I can feel them touching me but can't move to get away. It's horrifying.
I have been attacked by a skull, a translucent man, square with a face, dragon and wolves.