Hi,
Base on my experience, Windows 8 will not shut down after Windows update, but restart instead.
I suggest to perform these tests to troubleshoot the issue:
1 Run
chkdsc /r /f and sfc /scannow
2 Reset Windows Update components:
http://support.microsoft.com/kb/971058
This should also apply for Windows 8
3 Disable firewall and security programs.
Hope that helps.
Leo Huang
TechNet Community Support
