Violent shaking of head. For your reply.

Hello Doctor, I am suffering from a strange problem which occurs only during my daytime sleep (it never happens at night). While in the middle of sleep I feel that I should get up but my body seems unable to respond and in effect I raise my head slightly, tilt it sideways and then stretch it to one side so much that it starts trembling. All this happens when I am still asleep but I am conscious of all these happenings occuring involuntarily. When I get up I do not feel any complications except for light tiredness sometimes. This has started happening everyday. I was recently diagnosed as being vitamin B12 deficient (115) and I am on medication for it. I have also noticed that my hunger has increased excessively and if I don't eat on time I start feeling very lethargic. Doctor, please provide me detailed description of what you think my problem is. Can it be epilepsy or a sign of brain damage. I am very stressed and am looking forward for your reply. Thanks.