Google Pixel

I have had this strange behavior randomly happen in the last 6-8 weeks I would guess. It took a couple of times for me to figure out it was happening on disconnecting from my car, as I'm typically going straight from unplugging directly to my back pocket with the phone when I get out of the car. Once I pull the phone out of my pocket to use it, it asks for my pin since it restarted. I did do a factory reset of the phone and it still happens and still just as randomly. I did the factory reset about 5 days before the June feature drop and it's happened once after that as well. I'm sorta lost on what would be causing this. Any ideas?