Just to clarify: the phone was inserted into an air-vent mounted bracket. It had cold air blowing on the rear glass. It might have got some sun through the windscreen, at times.
I was using it in Android Auto mode, connected to the USB port in my car. So, charging, GPS, playing music, navigating.
I've driven over 10k miles with the same phone, using the same software, same use case, in all seasons, all times of day, and this had never happened before.
My previous phone, an LG V35, never overheated, ever. Not even in the hottest weather, in direct sun. Despite LG's rep, that was a great piece of hardware. It survived being immersed in floodwater for 12 hours, continuing to function well for another two years after.
Overheating did, however, happen pretty frequently with my previous phone to that - a Blackberry Priv - pretty much whenever the phone was both charging and in use. Or if the camera ran too long. That model was a total mess. Wasn't sorry when a drop shattered the glass into splinters.
If someone wants to find another excuse for Google, please have at it. People are really simping for Google? Really?