How to make a pc enter Sleep after power failure

Question

My question is the following, I want my PC (windows 10) after a power failure back on automatically but... if I’m not using the PC at the time I want it to go into Sleep mode.

In my head it’s easy:

1- check that the pc came from an offline status 2- wait 3 min and check if someone has logged on 3- if this does not happen put the pc in Sleep mode

some advice how to do this?

Thank you