I'd wake up from a bad dream, and couldn't move. I wasn't completely awake, but aware of my surroundings and realize I couldn't move. It was like something was sitting on my chest
I've had that almost identical experience on a couple of occasions. Half-asleep, but aware of my surroundings, feeling like something was on top of me. I even thought I heard whispers, and could see shadows in the room. Like you, I just chalked it up to the fear of demons instilled in me by the JW religion.