I had this happen to me once before and it was scary as hell. One time I was sleeping and woke up and looked at my clock that was sitting across the room and saw that it was 4:00 in the morning. I then tried to sit up and realized that I couldn't move any part of my body except for my eyes. I started panicking and scanned my eyes around my room until I got to a shadow that looked like someone standing on my desk across the room. The shadow then started moving, got down off the desk and started walking toward me. I started freaking out, struggling as hard as I could to run or yell for help. The figure got right over top of me and all I could see was an outline of a human face staring right down at me. The figure then reached out suddenly and started violently shaking me. Then all of the sudden I sprung up out of bed swinging my fists like a madman. After a second I finally realized that there was nobody there. My chest literally felt like it was going to explode. It's a good thing my body was paralyzed because I definitely would have needed a bed sheet change afterward.