Leg mussle spasm. I watch my mussles twitch and move - I cannot stop them but does it matter?

Leg muscle spasms. Leg muscle spasms can be caused by an overused, overstretched muscle, dehydration,  depletion of electrolytes, medications or various medical conditions. try to gently stretch the muscle back to length to break the spasm cycle. If you are trying this and unable to stop it, it is particularly concerning, you should be evaluated by a physician.
Many posibilities. You may have a deneurvation problem, electrolyte imbalance, drug toxicity, heavy metal poisoning, ... See your doc , treat this serious.