The Last Two Nights I Go To Sleep Fine. About

The last two nights I go to sleep fine. About 6 hours after I've been sleeping I wake up with the room spinning and I have to remain sitting. The moment I try and put my head on the pillow the room starts spinning at such high speeds. Its happened two straight mornings now. I will see what happens tonight. Physically I feel great and don't suffer from anything. Don't understand whats going on?