Our servers do regularly restart as they need to install Windows security updates, sometimes at relatively short notice. There’s a scheduled restart on all the servers at 2.00 am NZST each Monday morning. Prior to the restart, anyone logged in at the time will receive a warning message on the screen 30 minutes and then again 5 minutes before the restart.
Additionally, sometimes critical security updates are released by Microsoft that need to need to be installed urgently. In these cases the server will still restart on the weeknight at 2.00 am NZST, and the same notifications will appear.