There are many causes for muscle twitching. Some of the common ones are stress and anxiety, too much caffeine, nutritional deficiency. smoking, alcohol and certain drugs like steroids and stimulants containing amphetamine. Rarer but more serious causes are a group of muscular deficiencies. Since you have been having this for a while, it makes sense to have a blood work up including thyroid levels and a neurological examination. Meanwhile, certain things you could do are eat a healthier diet containing fruits and vegetables, avoid caffeinated foodstuffs and coffee, stop smoking if you do and reduce alcohol consumption, prevent dehydration and increase potassium intake commonly found in bananas, substitute drugs containing amphetamine after consulting with your prescribing doctor and lastly, reduce or find ways to avoid stress.