My 2005 Limited edition Z4Roadster has a problem that the shop can not duplicate. As I was entering my drive way the car made a large clunk and banging sound. It stopped dead and would go into gear. When the tow truck came to get it, it started and went into gear just fine. They have put it on the computers, said the transmission was fine. I am afraid to drive this car. It has made this noise before and they could not find a problem. I am afraid to drive his car. If it happened on the freeway I would be dead. What is going on? Help