> What is log_min_messages set to? Increasing it might shed some light.
It is not set (commented out). I assume the default is "warning". I will set it to "info" and see if that reveals anything.
> Then check the recovery tab and see what it is supposed to do on failures - you are probably at the "Do nothing" count limit, hence the no auto restart.
I had already changed the recovery options to restart on first and second, then run a command script that starts it on the third count. None of them appear to work, which means the shutdown appears to be "normal" to Windows. Or maybe postgres doesn't set exit levels for Windows to act on.
> I see this sort of thing on Windows I immediately suspect Anti-Virus software.
This is what I suspect also. This server was recently "taken over" by a third-party management firm that corporate dictated, and they have loaded all kinds of monitoring and security crap on it. I have reached out to them but not gotten a response. I will push harder on this.