Ang, I had the same kind of experience when I was in my late teens or early twenties. I was lying in bed looking out of my darkened bedroom into the lit hallway. I thought I saw my sister come down the stairs, but her "head" wasn't well defined, as though she had on a space helmet or a fish bowl. Next thing I knew the figure (who I guessed by then wasn't really my sister) came in through my bedroom door towards my bed, until it was at the side of my bed, looking down at me, head still undefined. I couldn't tell if it was an alien or a ghost, or something else entirely. I freaked out and started kicking at it, but I couldn't seem to move. In a blink (perhaps I was startled "awake?"), the figure was gone, and I was alone in my room, kicking at nothing and frightened half to death.