Prevent Windows restart after updates

Navigate to:

Windows \ Run \ gpedit.msc \ Local Computer Policy \ Administrative Templates \ Windows Components \ Windows Update

You should enable No auto-restart with logged on users for scheduled automatic updates installations and optionally enable Re-prompt for restart with scheduled installations with maximum value 1440

For policies to take effect you may run gpupdate /force

To check is policy applied you may run rsop.msc

If restart prompt still opens you should restart Windows Update service or restart your machine.