This has been happening to me for about 2 years now. It only happens on occasion. Usually when I am very drowsy or tired. For example, when I am up very late studying, wake up early for test, and then return to my dorm and take a nap. I am sure to feel these strange sensations. Let me try to describe it. They last a very short time and seem to accompany individual heartbeats although they are sometimes strung together. They are accompanied by ringing in my ears and what seems to be a pressure on my eyes. The feeling is rather pleasurable... it's a sort of euphoric feeling or a feeling like my head is suddenly floating. It is very hard to explain. I have looked everywhere to figure out what this thing is. I hope someone can help.