Hi have serius is problem for mi new Fairphone 5 have problem for Android auto and bluetooth car crashed and reboot my phone continus cable or not is same problem no idea is problem hardware or glitch software 
I’ve had a reboot happen once, but I thought it was due to my clumsiness and accidentally tapping the wrong things while fiddling with the phone and cable.
With another phone I had there was the problem that the holder of the phone in the car sometimes accidentally activated the power button when the phone wasn’t inserted perfectly straight. It kept the power button pressed the entire time which resulted in rebooting all the time.