Windows 10 updates automatically when restarting it. How can we prevent it, and what else can be done?

In order to prevent automatic updates, you just need to disable them. Do it by following this post.

Besides that, you can check for updates when you don't work on an urgent issue on the machine, because the update process may take a long time (sometimes it takes hours!!!). Please notice that most of the updates are security updates and should not be prevented for good, and better apply as soon as possible!