No shit man, this happens to me often. It's a phenomena called sleep paralysis in which the bodies motor cortex is not functioning, but the eyes are perceiving vision as though it were awake. This being said the mind is still half asleep, causing what I have taken to calling the black one to appear near my bed. I can't move, and I can't scream for help. Look it up if you want a better or actually medically accurate explanation.