IS THIS BAD? AND DO I NEED A DOC? 10pts?!

Well anyways after i do heavy exercising and i go to lay down and rest all of a sudden out of no where my calf musles tense and waves of pain start hitting me wen i look at my leg it looks as if something is alive because the musles move side to side then suddenly it just stops this only lasts for like 2 mins tops but it hurts like hell is there something terribly wrong? btw this has happened 3 times before like only once a week..