Flight Simulator seems to impose enormous stress on machines and cause overheating. Running the GPU flat out in all the menus doesn’t help (I now limit my FPS in NVIDIA control panel to 60 to limit this). If you have any way of manually controlling your fans I would try turning them up all the way before starting the game, or see if the game will run for longer with the graphics settings turned way down and an FPS limit on. If that improves stability then probably you need to run lower graphics settings or improve cooling overall. I’m pretty sure the game trashed my last PC, it was old, my cooling setup wasn’t great and it was a bit underpowered for the job - after a few hours of playing I was getting full system crashes to the point where the machine wouldn’t even reboot until it cooled, and it mysteriously kept corrupting the C drive. Once it started doing that outside of gameplay I concluded it had damaged something and it was time to get a new and powerful enough PC.
However, I’m being quite pessimistic here! When windows crashes in its entirety there is often something left behind in the event log, and you can force windows to write a crash dump file which can be analysed afterwards. Either/both can be diagnosed to try and work out whether its something like a driver crashing the whole machine, or might point at a failing hardware component. Looking at the event log (event viewer) is easy enough, reading crash dumps is a bit more specialist - you can google advice on how to do both.