Apparently Alt Tabbing from the game is not well liked by Fallout 4. You are able to Alt Tab out of the game, but alt tabbing into the game causes a major sysem issue.
What happens is your screen will suddenly get locked out. Either no longer detected by the operating system, or perpetually stuck in a blank state that requires a reboot.
I somehow got the worst of it, which actually caused Windows to fail to detect the monitor that is attached to. Even if I rebooted, Windows would not detect it. Keep in mind that I get the post screen and everything, but the moment I get past Windows 10s loader screen, it stays dark. I had to forcefully reboot the computer several times to force windows into a repair menu just so I can go into safemode to fix it.
To Bethesda, please read this post and fix it. Not everyone is savy enough to get their computer back up and running again.
To consumers, avoid alt tabbing at any cost. If you must, save and turn the game off first. If you alt tabbed out, kill the game with Task Manager.