Are you taking any medicines or supplements? How long has it been going on? Is their a trigger event?
Their are numerous causes of muscle-twitching. Most of them are short-term, and cause no problems/require no treatment. One common cause in benign fasciculations, and it is often caused by medication or supplements (remember herbs are supplements to).
If it has been happening for a while, I would recommend you see a doctor. It is probably nothing, but their are serious conditions (mainly neurological) that can cause it, and some of them are degenerative.
If you post more information, I can try to provide a little more detailed information, but I will still recommend you see a doctor.
Good luck.