Engine Belts And Pulleys problems of the 2017 Kia Motor Optima

Bought on 9-12-2019 with approximately 15,400+ miles. It now has 15,750+ miles. It has stalled/powered off on me twice. First time was oct 7, 2019, parked on the curb when I was picking up my daughter from school, when she got in the car and I was about to drive off from the curbside and when I lifted my foot off the brake and stepped on the gas, the car wouldn't move. I realized the power off so I switched the ignition to off and turned it on again to start the engine again. I thought it was just a little glitch. It happened again on oct 26, 2019 when I was on the drive thru of taco bell. I was waiting in line and again, when I lifted my foot off the brake to move forward, it wouldn't move because the power had just shut off again. I had to restart the engine. I complained to my son about the car but didn't do anything about it because it was past the 7 day exchange or return. But planned to bring it up on my scheduled maintenance unless it happens again. I was always cautious and worried that I will stall in the middle of traffic or worse, while driving. Mostly the reason why I've only driven the car less than 300 miles since I bought it about 4. 5 months ago. Then yesterday morning, Jan 28, 2020, on my errands to two doctor appointments, the passenger seatbelt sign was beeping and flashing the whole time I drove around that day, when there was nobody with me in the car. It finally stopped when in the afternoon when I was close to home and after I picked my prescriptions from the pharmacy close to my house. Now I am curious and wondering why the navy man traded this car in when he'd only had it for la year and spent money on new black rims and blacked out tinted windows. I would like to have an inquiry on what problems the previous owner had with the car because of the short time he owned it and drove it. I'm more terrified to drive after reading other's issues.