Rather annoyingly, officebackgroundtaskhandler.exe flashes a popup every hour. This is due to a triggered task in the Task Scheduler flashing a popup window for the officebackgroundtaskhandler.exe process, which seems to be part of the Microsoft Office 2016 suite.
To fix this, I tried altering the scheduled task to tick the “Hidden” box, but that didn’t work.
Others on the internet have either disabled the task or changed it to run as the SYSTEM user account, so it won’t start in your user context. If the officebackgroundtaskhandler.exe process actions things in it’s current user context then changing the run as user to SYSTEM is effectively the same as disabling the task.
I’ve not been able to find out what officebackgroundtaskhandler.exe is for, but if you do please leave a message below.