Hi there,

I have had similar experiences to this. It sounds a lot like sleep paralysis, this can do the sort of things that you are experiencing. In a sense it is like your mind is awake but your body is asleep. You can't move and you panic not realising why and sort of hallucinate imagining that someone or something is there holding or pinning you down which is about the only rational thing you can think of why you are unable to move when actually your body is asleep. It normally happens to me when I start to wake up in the morning but not sure of it happening suddenly??