I guess the experience I had occurred about five years ago in the house that I now currently live in. I remember it being a humid, warm, summer night (which usually is in East Texas) and I had just gone to bed and dozed off quickly. The next thing I knew I awoke sometime later and felt as if something was sitting on my chest, something extremely heavy and it was pinning my shoulders down to the bed. I opened my eyes and to my surprise this thing appeared to be even darker than my room, as if this thing denied any light at all. It had the form of a human but I could not make out any features whatsoever, as if it was a silhouette yet it had substance. As it had me pinned down I felt totally paralyzed. I broke out in a sweat and then all of a sudden as if it was never there, it was gone. I don't know if it was just a waking dream or what but it felt too real to be a dream. Perhaps it was a dream because that is the only thing like this that has ever happened to me. But I'm still open minded enough not to rule out that it could have been supernatural or spiritual.
See the page on Sleep Paralysis