Turn GUI Off with PowerShell
Get-WindowsFeature *gui* | Uninstall-WindowsFeature –Restart
Once rebooted, you will only have the command line and no GUI
Turn GUI On with PowerShell
Get-WindowsFeature Server-Gui-Mgmt-Infra, Server-Gui-Shell | Install-WindowsFeature –restart
Once rebooted, you will have the GUI