Windows update service can be started from command line(CMD) using the below command. Make sure that you open elevated administrator command prompt to execute this command.
net start wuauserv
C:\Users\Administrator>net start wuauserv The Windows Update service is starting. The Windows Update service was started successfully.
Update service can be stopped using the below command
net stop wuauserv
C:\Users\Administrator>net stop wuauserv The Windows Update service is stopping. The Windows Update service was stopped successfully.
Note that on Windows Vista and Windows 7 machines net start/stop commands should be run from elevated administrator command prompt. Other wise you will get the following error.
C:\Users\administrator>net stop wuauserv System error 5 has occurred. Access is denied.