Unlikely you completely shut off the vents while driving, which would pull outside air in to cool it. Just opening the door to get inside will cool the car quite a bit. If you want to see what happens when the car is parked in the sun without driving, put a thermometer in the car and park it in the sun and see how hot it gets. I don't recommend actually sitting inside and trying it out for yourself, because you could actually pass out and die before you realize it.

https://duckduckgo.com/?q=child+dies+in+hot+car&t=ffab&ia=web