Hello Mr.Belong, and welcome to Seven Forums.
You could use the tutorial below to disable Windows Update from automatically restarting the computer. This way you won't loose anything anymore.
Windows Update - Enable or Disable Automatic Restart
Next, double check to make sure that you have the install new updates time is set to when you like.
Windows Update Settings - Change
Next, double check to make sure that you have "install updates and shut down" enabled to have updates (if available) install when you shut down.
Shut Down Windows - Enable or Disable "Install Updates and Shut Down"
Hope this helps,