How to prevent automatic updates from restarting your pc without permission?

Some features in 10 are really a headache, one is the one you mentioned and second is software search option is lame. It was better in 8.1. Sorry for the OT. I don't have the answer to your query.

 

Option 1) The easiest and most common is to change from Automatic to Notify to schedule restart in the Advanced Options of Windows Update

Option 2) If you have Pro/Education/Enterprise then use the following reg tweak to change Windows Update to not download nor install any updates but to nag you that there are updates ala Pre Windows 10 and give you the Download button so you can download and install updates at your leisure.

Option 3) Disable the Windows Update service and only turn it on when you are ready to do updates:
Disable Windows Update from the command prompt (requires Administrator permissions):

Re-enable Windows Update from the command line (requires Administrator permissions):

Turn it back off (requires Administrator permissions):

 

Option 2 only works if you do not manually 'Check for Updates' in the WU menu. You have to let the system find the updates on its own in order for updates not to be downloaded and auto-installed.

 

there was the shutdown command i used too "shutdown -a" if i recall, i had an win7 update who forced a reboot, i blocked that ...

 

Yeah, I had mentioned that in a few other threads but forgot to in this one.