it depends on your configuration of "Scan and repair settings" in patch manager.
In the "Reboot" tab of "Scan and repair settings" dialog, you can configure if the user get a message, if the user can snooze the reboot (and how often), how many times the user get the message, if the user can cancel a reboot, etc.
And you can set "Never reboot". But if a file is in use and a patch need to change this file, a reboot is necessary.
Normally no automatic reboot will be made, but I've seen it ...(no differences between the different patch management software solutions: WSUS, LANDesk, Shavlik, ...).
It depends on the patch creator/vendor, the software which is patched, if a basic OS file is changed, etc.