I Have A "buzzing" Sensation Near My Tailbone On My

I have a "buzzing" sensation near my tailbone on my left side. It is rhythmic and happens quite often. It lasts about a second or two each time. It has been buzzing for the past 3 days or more. What could it be? At first, I checked my phone to see if it was in my pocket or on the seat. It isn't my phone. It is me.