Mine does this on a cold start. When I start the car and turn on A/C (something you have to do right away when it's 105 F outside and 120 F inside), after I start driving, first stop I come to rpm dips to like 300, car shutters, ECU kicks them back to like 1100, they go down to like 900 and stay there. Only happens during my first stop. Yours might be having some wiring issue. Try to catch it on a video, then go to the dealer and show them everything.