This happened to me when I was about 12 years old. I'm 22 now and to this day I still can't explain what happened to me.
I was lying in bed one night trying to go to sleep, and I remember that night because I couldn't sleep for some reason and usually I pass out in about 5-10 minutes. So I was lying there with my eyes wide open, when all of a sudden all of my bed sheets, blankets and covers flew off me almost as if someone tore them off from the bottom of the bed. I was so terrified I just laid there silently for about 5 minutes until I finally ran out of the room screaming for my parents.
The odd thing, though, is that I went back in there to sleep the next night, and nothing. Nothing like that has ever happened to me again since.
Before then, however, when I was around 6-10 years old I heard a voice calling my name on many different occasions that sounded like my grandmother. It was always very late at night and I was trying to sleep but couldn't. Whenever I went to her room she was always either asleep or told me that she hadn't been calling my name.
I have no idea if these events are connected but it always happened when I was trying to sleep but couldn't. Normally I'd say it was an overactive imagination when I was younger but the sheets flying off the bed were very, very real. I know I was wide awake when it happened. It was definitely not a dream because I remember everything vividly, and I remember running to my parents room when I finally gathered enough courage to leave my bed. But nothing's ever happened since, and weirdly I've never been afraid of whatever it was even after the sheets flew off me.