What you’re describing sounds like muscle fasciculations (brief episodes of twitching). There are a number of things that can cause fasciculations, including fatigue, smoking, caffeine intake, certain drugs (anticholinesterases, lithium), electrolyte imbalance (low potassium, low magnesium, and low sodium), and disorders of the thyroid gland. There are also less common but more serious causes including a few types of neuromuscular diseases. Try to reduce your caffeine intake, take a daily multivitamin, and increase your intake of fruit and vegetables (green vegetables for magnesium; cantaloupe, bananas, or watermelon for potassium). If the twitches continue you should see your physician who may want to do some lab work and an imaging test.