I have a 2003 Cadillac CTS. Yesterday while driving it had stopped. After about 20 minutes we were able to start it no problem and drove home. This morning we went for a coffe and we couldn't come home with it. It stopped again and would not restart for 40 minutes, then it worked for 5 minutes and stopped again for 20, worked for 6 and so on. I had it towed.. Anyone knows what this might be?