Some of the issues are very frequent in windows 8 which needs serious attention.
1. Service gets hanged at starting or stopping.
2. stuck at restarting
3. Unable to install any application due to system files corrupt.
Check if there is any service which is in stopping state and having difficulty in stopping.
Check if there is any programs which is stuck while restarting.
Check if Antivirus is malfunctioning or outdated.
Which worked out in my case is to Uninstall the Trend micros office Scan Antivirus will solve the issue.