imac doesn't shutdown on catalina
Catalina 10.15.2
iMac is now consistently (but not constantly) failing to shut down - all icons disappear just freezes with my desktop picture, sometimes all night because I thought it shut down and find out next morning it didn't.
are there logs or something I can look at or do to resolve this.
iMac with Retina 5K display, macOS 10.15