I just finished 2 years of nursing school and to be honest with you, that actually sounds alot like what we call Sleep Paralysis. leep paralysis is a condition characterized by temporary paralysis of the body shortly after waking up (known as hypnopompic paralysis) or, less often, shortly before falling asleep (known as hypnagogic paralysis).
Physiologically, it is closely related to the paralysis that occurs as a natural part of REM (rapid eye movement) sleep, which is known as REM atonia. Sleep paralysis occurs when the brain awakes from a REM state, but the bodily paralysis persists. This leaves the person fully aware, but unable to move. In addition, the state may be accompanied by hypnagogic hallucinations.
More often than not, sleep paralysis is believed by the person affected by it to be no more than a dream. This explains many dream recountings which describe the person lying frozen and unable to move. The hallucinatory element to sleep paralysis makes it even more likely that someone will interpret the experience as a dream, since completely fanciful, or dream-like, objects may appear in the room alongside one's normal vision.
In some cases, when hypnogogic hallucinations are present, people feel that someone is in the room with them, some experience the feeling that someone or something is sitting on their chest and they feel impending death and suffocation. That has been called the “Hag Phenomena” and has been happening to people over the centuries. These things cause people much anxiety and terror, but there is no physical harm.