Battery Cable problems of the 2014 Cadillac ATS

54,189 miles on car currently. Since June of 2019 my car/engine will completely shut off at a red light, or a coming to a stop sign (basically completely stopped or coming to a stop). Its even shut off while in reverse. When this happens, the gear is still in drive. So I then have to put the car in park,press the brake and start it again. It sputters to start again, but it starts. Its getting more frequent, with it stopping up to 3 times at one stop light, and then having to restart it again. There are no codes on the dash. Ive brought my car into crest Cadillac multiple times to try and diagnose this issue. They cannot find the root cause, and it still happening most recently today! there is a new battery, alternator testing in good condition. They have tested the battery cables/lines. This is incredibly frustrating. My car has stopped on me when trying to accelerate and turn into a lane and I was almost hit bc my engine completely shut off. I also called gm and was told without a diagnosis they cant help. Ive spent so much money on diagnostic tests with no answers. I need help please.