Isolated twitching in your thigh is probably nothing to worry about. It's little muscle fibres firing away at random. The most common triggers are fatigue (lack of restful sleep), dehydration, stress, anxiety, over-exercised muscle, a diet deficiency or a drug side effect (such as diuretics, corticosteroids and estrogens)
Many people experiencing these symptoms fear they may have MS, or some other neurological disorder. A simple clinical rule is that twitching in relaxed muscle is NEVER indicative or motor system disease unless there is an associated weakness, atrophy, or reflex change.
So try to relax....I had a thigh twitch that lasted a couple of weeks ....drove me nuts.....and then one day it just stopped as suddenly as it started.
Make sure you are getting enough water and take a multivitamin daily in case you're not getting enough potassium, calcium or magnesium in your diet.