Once in a while when I start the car it dies and jerks and sputters. White smoke comes out of the exhaust with a heavy sulfer smell. The check engine light and ESP malfunction lights come on. If I start and restart the car numerous times and drive it limping and jerking for a few minutes and then restart it it runs like a charm. The malfunction disappears and the check engine light stays on for about an hour and then goes off. This only happens on cold starts. Techs at dealer find numerous error codes but cannot replicate. HELP!!!!!!!