Suggest Treatment For Feeling Of Vibration In Knee

Periodically throughout the day my knee feels like it is vibrating. It is not constant but I will feel a vibration (like a vibrating phone but fainter), it will happen for a few seconds and stop and then start again. I havent counted but I would guess that it happens anywhere from 10 - 20 times a day. What do you recommend I do, what kind of doctor should I see? What could possibly be causing this?