I woke up throughout the morning with severe dizziness, room was spinning very fast, no nausea. never had this ever. what is the cause?

Labrynthitis: Most likely cause is labrynthitis - a viral infection of the inner ear. If no other neurologic symptoms (headache, blurred vision, slurred speech) - unlikely to be anything serious. It could also be benign positional vertigo. Both of these are self limiting and will get better. Either way, it would be a good idea to see your primary care doctor. If there is any hearing loss... See your ENT asap.

Viral labrynthitis: A viral infection of your inner ear. Typically very sudden and severe. Best treated acutely with steroids and valium. With steroids the symptoms resolve quickly.