Muscle twitching is just involuntary (meaning not on purpose) contraction of a muscle. It can be caused by many things. In young healthy people it’s very common after exercise, or right before or after sleep. It’s also very common in the muscles around the eye after exposure to bright light. Sometimes it happens more when people are stressed.
Muscle twitching can be due to dehydration or changes in your blood chemistry, especially after exercise. If you find that it’s happening often after exercise, be sure to drink plenty of fluids containing electrolytes. If the twitching is uncomfortable, happening very frequently, or associated with other problems such as trouble thinking or seeing, please be sure to see your health care provider.