Power Train Driveline problems of the 2008 Lexus LS460

We've purchased a 2008 Lexus 460 on Jan 2008, within few months we started noticing a jerking reaction of the engine while the car was stopped or idling in gear most of the time. Over time we've taken the car to the dealer (at least 4 times) with no substantial improvements, they've upgraded the transmission software checked it out and could not come up with a fix. The last was in November 09 and we were told to contact the CO. Fo factory rep to inspect the car. So far they have not inspected the car and we are afraid that it may cause to an accident.