Brake Sensor problems of the 2016 BMW 328

I was slowing down to approach and stop at a red light on a street (not highway) and my car wasn't braking. It then stopped. After it braked and I was sitting at the red light with my foot on the brake fully stopped and stationary for approximately 10-20 seconds my car accelerated without warning and hit the back of the car ahead of me. The impact caused a tiny scratch on the drivers bumper from my license plate. His car was old and his bumper already damaged, so he wasn't too concerned about the scratch. We pulled off to a nearby parking lot and he checked under his car and under my car to make sure there was no damage other than the small scratch and we parted ways. I called the my BMW service center first thing the next morning and brought my car in. Two months prior to this incident, my car stopped without warning on a street with no traffic when I was traveling at approximately 20-30 miles per hour. I assumed that something set off one of the sensors, but this is not a street where people or animals would be crossing and no one was in the street. Their corporate headquarters in NJ sent in a field representative and inspected the car. An executive customer care representative from BMW's NJ corporate headquarters got back to me yesterday reporting that they could not find any issues with the car and I can pick it up at anytime. They could offer me no explanation for this occurrence and I am terrified to get back in this car. I am estimating the mileage on my car as 25,000 miles as my car is still at the BMW service center and not in my possession to check the exact mileage.