A very annoying and worrysome problem. I have had a twitching lasting anywhere from a half min. to a min. and a half. This goes on forty or more times a day! It started in my eyes, now the muscles in my left arm, the calf of my right leg, my buttocks and even my shoulder and neck area. Also feels like I get heart palpatations the last few days (mostly at night) while sitting and not doing anything to bring it on. I am 64, lost weight recently noy on purpose, weigh about 115 lbs. and I am 5' 5".
I have a Dr. Phisical coming up the end of the Mo.
Thanks in advance. Sorry I went on so long but wanted to explain everything.

Twitching muscles can be caused by an imbalance of sodium/potassium. This may have been caused by you recent weight loss. Eat something like cheese with a few salty crackers. Then add potassium with tomato, kiwi, orange or the trusty banana. I'd go to see the doctor and have blood checked before the end of the month. Medications you are on may be influenced by dietary changes, this needs to be discussed with your physician right away

Yeah I take potassium or eat a banana or baked potato at bedtime because I get the twitching and leg cramps when I am trying to fall asleep.