Its called Sleep Paralysis... some-say its spirits who are trying to contact you... evil or good. I remember having thouse everynight, I would be surrounded by black figures and they would make me stab myself with knifes and shit... FUCKING scared the living shit out of me cause you cant move... It seems as if something is holding you down. But I keep trying to move and when I finally have enough will power to move its as if it wasnt a dream and Im awake...