It has absolutely NOTHING to do with blood circulation. It is called neuralgia and it is because of something going on with nerves. You can sleep wrong on your arm or hand or whatever... and feel like your limb feel "asleep" If you pinch a nerve or work too hard and put stress on the nerves these types of things will happen. It is usually a part of getting older.
I'm 35 and had a similar problem. My hands were numb and I felt as tho one of them was swollen. I went to the chiropractor because I was getting dizzy too. After one adjustment all my hand problems went away. I go one e a week and I haven't had the problem since.