I went thru a period wherein I suffered those almost nightly for a period of a month or two. It was terrifying for me so much so that I made my boyfriend at the time come stay with me and I lived in another town than he.

I didn't see anything at all but I was wide awake and completely paralyzed and tried with all my might to scream but of course wasn't able to make a sound. the moments seemed interminable when I was in that state, and when I was able to escape it I didn't want to even try to go back to sleep. I knew whatever it was it would happen to me again if/when I did, or so I imagined.

Everytime it happened I was wide awake when it stopped, so I'm not sure I was ever asleep at all because I never experienced it and then continued to sleep, ever.

It got to be a rough row for awhile there but then it stopped and I haven't ever experienced it since.

I didn't see anything but for some reason I knew or had the sensation that something was holding me in this state of complete paralyzation. Dread fear, naturally.

It wasn't long after these episodes however that I actually started having out of body experiences while my physical body was asleep. I have since been told that when we are just beginning to learn to project our consciousness out of our bodies while sleeping that one of the things we go thru is this effect of being paralyzed, seemingly because we are just out of our body enough not to be able to make it function but not having actually lifted out of it enough to be able to look back upon it on the bed and see it from elsewhere, hence still in it but not connected so to speak. When you have an out of body experience you can see your "light body" as you move around in it and you can also see your physical form on the bed when you stop whatever you are doing and return to it.

I never did know what caused it, that's just some of what I had been told regarding my experiences with it.