Starter problems of the 2020 GMC Terrain

We drove to a farm with a family of 5m kids and an elderly, and parked my car for 2-3 hours in the farm's open area parking lot. Vehicle showed no warning lights, no problems, no issues during our drive to the farm and prior to this trip. Everything was fine when we go there and parked. We were ready to leave the farm to drive back home, but the car simply wouldn't start. The neutral gear didn't work, I attempted many times in 30 minutes to start the car, but it didn't start, continued making the sound of engine attempting to start but not suceeding. 30 minutes later, I decided to give it another try, I was afraid to burn down the starter after attempting so many times. It sounded terrible, screeching metal sound. All of a sudden, the car started. I let it run, afraid to turn it off again. After 15 minutes of running, while we were waiting for roadside assistance to arrive, the vehicle turned off again, all by itself. No one was inside the car, we were waiting outside with the driver door wide open. I called roadside assistance, waited 40 minutes to get a live agent to talk to. The yellow engine light is on. I tried to look in the manual to be able to find anything remotely close to what was happening. Came up with nothing. This was so far the trickiest thing to happen to me. I scheduled an appointment to take the car to the dealership for diagnosis.