I have a 1999 E320 4Matic, when I start the car in the morning or after it sits a while it starts immediately, when it is hot and i park the car and try to start it 15-20 minutes later it will crank but not start. I left it with my mechanic for a week, he could not duplicate the problem, of course after I took it home and stopped at the store for 15 minutes, came out would not start, left it sit at the store overnight, started right up. It starts every morning when heading to work and every afternoon when going home. Any idea?

Haru