This sounds like what is sometimes called "sponteneous gong" or "sponteneous movements". It often means that there is qi blockages that are starting to move or become unblocked.
I have had this happen from time to time. I even used to practice a qigong form that actually encouraged this at the end of the entire form during standing meditation. And another one where the standing form was primarily sponteneous movement (there was only "form" at the very beginning preperation).
Let it be and relax. Most likely eventually it will eventually subside. The movement of qi or energy becomes more subtle over time.
That's my two cents or whatever it is worth.
