CODES

Coming off the line the car will jerk into gear took it to GM they look at it from bumper to bumper can find nothing, When the car engine is warm, tranmission temp is between 198-201 and in stop and go traffic it will start, stop the car turn it off it stops. Maybe happen again in a day, weeek, month. No codes, no check engine light. Tranmission fluid flushed and changed in June 2012. I have maintained my car regular oil changes, tune up, tires, brakes, etc. I do notice that the engine temp will raise a bit but if you turn on the AC it drops. Any suggesttion or do I just need to wait to see a check engine light or hard failure? Thanks janis