This one:
I never heard about that brand. But it has a 85 plus label, this label is probably a knockoff/ripoff of the 80 plus label.
I wouldn’t trust that one…
I would say it’s likely the culprit here. Like the others said, MSFS is probably the “game” that uses the most our hardwares. The other games not causing it don’t mean MSFS is the culprit.
Try to use one of those benchmark softwares like AIDA64.
Did you check individual core temps or the 60 degrees is the average CPU package? they could differ a lot…
I agree with other, a sudden shutdown is an hardware problem, even if it only happen in MSFS. You can have a sudden raise of temps regarding CPU or GPU and all shutdown by security because cooler system can act enough quickly. I repair a lot of computer (part of my job) and the last one was due to the GPU going from 30 degrees to 107 degrees in less than 3 seconds, and PAM, complete instant shutdown. I redid the thermal past of the GPU and it was fixed.
I noticed that the LED lights of the gpu connectors light up and after a few minutes the PC turns off! I thought it must be a PSU problem … Next week I get the new Psu … a 1200w from the coler master 80 platinum brand! Yes I know … 1200w is a lot … But I took advantage of the discounts
Good move! 
And anyway, having a more powerful PSU will not change your electricity bills as PC parts only take what they need from the PSU. At least every component will be now well served.
I was one of those wondering if your PSU was the problem. I really hope it sorts out the issue for you.
Is there any chance of you coming back here in a couple of weeks and letting us know if things have improved for you? Some feedback would be great even if it proves some of us, including me, were way off track ?
Ok … It seems that I have solved the problem … With the new PSU (Cooler Master 1200 platinum) the PC works perfectly … No more shutdown with FSM 2020 … the PSU is the heart of the PC … It must always be done a great buy for this component! Thanks to all of you for your help … See you in the skies … Have a nice flight every one… 
Nice to see you’ve fixed your issues. Enjoy flying!
Thank you for taking the time to come back and reporting the solution.
Glad your PC is now okay.
Glad to here. Not to worry we are here to learn and the flight sim community has also taught me a lot about PC hardware. Been where you were with my PC shutting off every time I flew on X-PLANE 10.Changing the PSU made all the difference