What can be the cause of vibration feeling in uterius /pubic bone area off and on?

Mechanical. It is hard to think of a cause of the feeing of vibration in the pelvic area (aside from the obvious) but one thing comes to mind. It is a long shot. Could it be transmitted vibrations from something you are sitting on. Does it happen only when you are driving? Is it really vibration or maybe rapid muscle twitching ?