About every 2 weeks, my car will start but will not idle and cut out. It will restart but again will not not idle and cut out again. Sometimes it will start and when I take off, it dies while I am driving. Other times it won't start at all and the battery completley dies. I have to jump start it to get it running. After jump starting, it runs fine until the next episode. I have a 2003 Jeep Liberty Sport. Help! Do you think it the battery or possibly the alternator?