My left arm muscle keeps shaking. it starts all of a sudden n lasts for few seconds. i have migrain n to be honest i lack in execrise. what is this?

SEE BELOW: Sudden focal shaking lasting a few seconds could be problem with brain irritability, perhaps a focal seizure, and needs to be fully evaluated ASAP. Discuss with your doctor.

Muscle fasiculation: This sounds like a muscle spasm or fasiculation. It can be caused by acute temperature changes, low calcium, low phosphorus, low magnesium, low iron, trauma,and/or perhaps your migraine medication. I would increase these vitamins in your diet, and also seek medical attention if the muscle spasms continue.