Unfortunately, the provisioning GUI is visible when somebody is logged in by default. If nobody is logged in, the system will wait 10 minutes to start the task even to wait if somebody will login to show the GUI.
Never tried to expirement with the scheduler to repeat devices provisioning every month. This should be pretty easy to test though, with a small template repeating every hour...
If you rename the provisiongui.exe, on the core server under ldlogon\provisioning\windows, to provisiongui.old, it will stop the pop-up window from opening.