Eu tive um problema parecido .
Por essa resposta :
...reset all the Windows Update, that way it will start anew. You can use this script. Run it As Administrator, use option 2 and 3, and when finished restart the PC.
If that does not help, I would suggest you trying to delete the registry key
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update\RebootRequired
(export it first to have a backup) and restart the PC again.