18.04 Monitor power down is spotty

I am having a problem with the monitor powering off after 30 minutes.......

Sometimes the monitor will power off and sometimes the screen will just stay on and the next time it will power off. This just started after I had my computer up and running for 26 days. And before that the monitor powering down was working fine no issues.

Any ideas why the monitor will sometimes power down and sometimes not power down? How do I fix this annoying issue?