I think it may prove to be a case of hypnagogia, aka sleep paralysis: you may see, hear and feel some really freaky things while almost awake (or asleep, but it usually happens while waking up) and at the same time, if you try to move in these instances, you may find that you can't. That's because of something your brain does, and it's usually triggered by lack of sleep and/or added stress... Sorry, since that's probably the case!