Computer keeps updating restarting
You might find that things are quicker if you move from a Wi Fi to a wired connection.
Read more: How to fix Wi Fi problems on Mac You may be able to fixing a stuck update by going to the Mac App Store, finding the software you are downloading, and pressing Option/Alt.
As soon as you see the rotating loading circle, press and hold the Power Button until the computer shuts off. Repeat this process a few times until you see the "Preparing Automatic Repair" screen. Now you want to let the laptop boot to the "Automatic Repair" screen. Click "Advanced Options" and then select "Troubleshoot". Here you want to select "Refresh your PC", if you do not wish to erase data, or "Reset your PC" to erase all data and restore your system. From here just follow the screen instructions until the recovery is completed.
Alternatively, you may see a white, grey or black screen.When you do so you should see the option to Cancel the download.Having cancelled the download you should be able to start it again, hopefully without any problems this time.Sometimes things get slowed down because the Mac is taking a while to install one file behind the scenes and that's thrown the whole update time prediction out the window.The Mac might have been stuck on 20 minutes remaining for the past two hours, but this doesn't necessarily mean it's not busy trying to install the software. This brings up additional information and more details about the amount of time still remaining for the install.