You can check whether your server is pending a reboot after patching using this Powershell command...
Get-Item 'HKLM:SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update\RebootRequired'
To enable automatic Windows Updates via Server Manager. (Screenshots from Windows Server 2012)
You can wait for the patches to be installed automatically in the maintenance window. Or you can instigate installation via these screens...
sconfig
6 (Windows Updates)
a (all available) or r (recommended)
n (close menu without installing updates)
get-windowsupdate
You can uninstall an update by going to Settings>Update & security>Windows Update>Advanced option>View your update history>Uninstall update.Â
WSUS
SCCM
ManageEngine Endpoint Central (previously Desktop Central)
TSSA
TODO: others