My 1994 Jetta GLS has this habit of stalling at random times. It started happening about a week after I bought it. It is automatic. I keep taking it back to the shop and so far they have replaced the ignition switch and tumbler, the radiator, and the computer but it still shuts off. Everytime it shuts off though, it starts right back up. It also will lose power and cut out. Could this be a fuel related problem?