While coming to a stop at the end of the exit ramp my vehicle bucked when trying to go from a stop into 1st gear. Eventually the truck continued in a forward motion. Then came to a stop light and once again from a stopped position by truck bucked and eventually went into gear and continued forward motion. Parked the car where it sat for 1.5 hours then went to drive the vehicle and it bucked again into 1st gear. Drove to a parking lot were we parked to get lunch. Came out started the vehicle backed out of the parking spot and drove forward to the exit of the parking lot. When trying to exit the vehicle failed to move forward. The car acted as if it was in neutral and only revving to high RPM’s. Removing the fuse for the Transmission Control Ignition allowed the vehicle to move forward but only in gears 1,2,3. I brought the vehicle to GMC dealership and they recommended a fluid service to determine if metal chips are in the fluid. That service was performed and issue remained. The Dealer has recommended a complete transmission replacement. My vehicle never displayed a warning lamp or shown symptoms prior to this failure. My vehicle has a 8 speed transmission which is known to be a failing part with Chevrolet and GMC. A new transmission is costing me $7900 plus tax on a 2021 with low wear and highway use.