I am receiving the following error in postgres log:
FATAL,57P01,"terminating connection due to administrator command"...
Surely there is more stuff in the log file than that. Maybe you could expand the scope of what you quote. And include timestamps.
How to resolve this?
There has recently been a spate of hacking attacks where the hackers shutdown the server after starting up their payload. I'm not sure why, as that will surely draw attention to themselves. Maybe it is to keep out competing gangs of hackers, or maybe their payoff is now extortion (rather than cryptomining which was very popular in the past) and so they want to draw attention to themselves (although evidently they would be failing at it, as you don't seem to know about their attempt yet, just its effect on uptime). Look for new tables containing ransom notices as their contents.
Anyway, make sure you aren't being sloppy about security. Change your passwords, especially for PostgreSQL superuser accounts, make those new passwords actually be good ones. Better yet, also prohibit non-local superuser connections in the first place.