Apple - How do I find the log for the shutdown process?
Instead of looking at logs, I would start by booting in verbose mode. (It will also shut down in verbose mode.) Just hold Command ⌘ + V at boot.
Check the console for the time of shutdown
In the terminal, go to
/var/log
Find launchd-shutdown.log that was last modified by your system at the time of shutdown and perform a more on it
more launchd-shutdown.log