Automatic Transmission problems of the 2007 BMW X5

When accelerating from a dead stop, the car does nothing when you step on the accelerator and then lunges forward. The sudden bucking and hesitation makes hard to control the car especially in bumper to bumper traffic. I live in a suburb of new york city and I drive in stop and go traffic at 5 times every week. This does not happen every time you accelerate, but mostly when the car is hot, like in traffic. The car performs fine when it is cold. The dealer has experienced the problem, and the car has improved, but it is still bad when it gets hot. The dealer and the manufacturer's representative refuse to do more than drive it around the block and the last time it was there they drove it while it was cold and it was ok. I have brought the car back to them six (6) times and they still can not fix this. I think this is an accident waiting to happen. The car is very hard to control in traffic and I am afraid that someday I might hit the car in front of me, especially when in traffic. My first complaint to the dealer was March 30, 2009 and the problem continues to today.