Car makes a big jump when starting in Drive unless you start very slow. It is even worse going from reverse to drive. My Pontiac Dealer has replaced the motor mounts without any good results. He has an exact same model on his lot that does the same thing. He has not charged me for last couple of inspections but he cannot fix it. It did not do this when new and has only 60,000 miles on it
He has given up???
I don’t know if he has given up but you should give up on him. Find an independent shop, this should not be hard to fix. You are out of warranty anyway.