Which operating system is your PC running? My first thought is it sounds like something from software is shutting it down, but that’s not a behavior I’d expect from Automation Runtime.
Is it only Windows, or do you have a Hypervisor system (Windows + Automation Runtime)? Do you see it turn off, or do you know of any programs that are running when the shutdown occurs?
I can’t think of anything at the hardware level that would cause the PC to shut down on its own, besides loss of power or someone pressing the “Power” or “Reset” buttons. The fact that it goes into a standby mode rather than powering off makes me think something within Windows is causing it, but it’s hard to say without more information.