Hi Serdy,
I have had the same thing. It appears they are called hypnopompic hallucinations. Some scientist in Canada research this stuff, and they say the feeling of terror and that there is something in the room with you are very common in this experience.
I found out I had sleep apnea (or something like it called upper airway resistance syndrome) and I suspect that the sleep disruption from breathing was causing the problem. When I stopped sleeping on my back, the hallucinations disappeared.
I suggest you talk to your doctor about getting a sleep study. Even if you are not overweight, and don't choke or gasp, you can still have breathing disruptions that are bad for your sleep and health.
Bookworm