I just finished my 5950x build with a ASUS Dark Hero motherboard, H115i Elite capellix AIO and Thermal Grizzly paste. I am not overclocking anything in bios (load optimized defaults). My Windows idle temperature are 39-45C and they are the same in bios as well. I have ran Prime95 Small FFts torture test for around 6 straight , and my temperature didn't exceed 60C.
Whenever I restart my computer from within Windows 10 I always get CPU Over temperature error. I immediately go into bios and look at the temperature, and it is always 49-55C. I have also noticed that within bios my vCore is always around 1.4-1.44v. When running Prime95 torture test it doesn't exceed 1.07v. If I reduce my vCore in bios to 1.31v, I never get this CPU over temperature error. When I am using Windows everything is rock stable. I don't get any errors when I start my computer from a complete poweroff state, no errors when I wake from hibernation, and no errors if I cold reboot (by pressing the reset button on the case) from within Windows. I only get this error when I select Start->Shutdown->reset/restart. I initially thought it was a Windows installation issue, but it was still there after reinstalling.
With PBO during stress testing with Prime95 my CPU temps reach 74C. Screenshot of Ryzen Master during stress testing Screenshot