Hello:

I have a 2000 Seibring with 130000 miles on it. Car ran well until it start to shut off itself. If I stop at traffic light it shut off. Sometimes I crank it and it turns on, but sometimes it doesn't. On the other hand If I go on the highwaythe tach goes to 700 rpms but doen't shut off but at the same timeif I press gas pedal it doesn't respond and 10-15 seconds later it goes back to normalagain.I brought it to the dealer to perform a routine maintenece (oil change, filters, spark plugs, wires, etc) and they say nothing was wrong with it. But the problem persist. No codes from computer, no check engine light on. The problem is still there. What could it be?