Engine Knocking Noise problems of the 2017 Chevrolet Malibu

I purchased 2017 Chevrolet Malibu in 03/ 2017 with approximately 7 miles at the ourisman rockmont Chevrolet, located in rockville, maryland. At about 20,000 (12/23/2018) miles I brought the car into the dealership to have it diagnosed as I had a near death experience when I was stopped at a red light & then tried to accelerate when the light turned green except the car stalled once the emissions portion of the car tried to kick in, it cut off and did not restart in the middle of a 4 way intersection. I tried restarting the car for about 0 mins until then finally the acr restarted again. This occurence continued to happen peiodically, I am not sure what the cause of this reaction, but I let the dealership know if every instance and broughtthe car in to be checked at 20,000 miles, 24,000 , 26, 000 miles & 27,000 miles. I was told by the representative "guy" that GMC was notified and that I shouldn't continue to bring the car there. That was April 2018. Unfortunately, the incident happened again while I was leaving the garage at work. Car cut off another car almost slammed in the back of my car due the abruptness of the car going out. The ssue has never been addressed by the dealership and during the most recent incident August 2018 I took the car in to advise them of this issue in addition to a knocking sound in the rear of the car. I was told in August 2018 that I am outside of my warranty and that I would be charged a diagnostic fee. My car has about 50,000 miles currently. That is neither here or there. As the original issue was never addressed when it was under warranty and I am not willing to lose my life trying to have this car repaired in a timely fashion. Instead I have spent hundreds of dollars in rental car fees as I am not comfortable driving in a car with an issue so severe that GMC was notified and still has not been to rectify this issue with my car.