the most common cause for an eyelid twitch (called myokymia) is either stress or lack of sleep, but some folks get it for no reason ("idiopathic"). a warm compress will stop it temporarily. i have also had success Rx-ing topical eyedrop antihistamines like optivar, zaditor, patanal & elestat. its an "off-lable" use (meaning those drug were not DESIGNED to treat it, nor do they claim to do so) but they work pretty well.
if it does not eventualy go away, you could, in fact have blepharospasm. thats damage to the facial cranial nerve from a former viral infection or old car accident or something of that nature. if that were the case, i usually recommend BOTOX injections, the same type of treatment some people use to reduce facial wrinkles.
good luck! and dont worry to terribly much, as this is usually not a dangerous or life/sight/eye threatening condition...