Every time I switch off my computer, I need to restart it before switching it off why is it happening?

I work on computer about an hour or so and every time I switch off my computer, I need to restart it before switching it off. I do not know why it happens? There is no virus in my system as I use Microsoft Essentials and it cleans my computer from any sort of malware or virus.

Might be there is a virus in your system because of the threats that present in your system this is happening. Do one thing just remove Microsoft essentials and install the latest antivirus full edition like Norton internet security they gives you a 30 days trial where you can scan the whole system for threats and it protects your PC for 30 days if you are satisfied with it you can buy a full version.

Say some antivirus like free edition or shareware version doesn't scan in-depth of a system where the threats still present and the system files will be effected so you need to know that free edition has only limited features in order to get rid of these types of threats you need to try these Panda  Symantec ..etc they provide trial version for 30 days and you can observe the change.

Many people don't know just they bought antivirus of dollars but the functioning and features were not known by every consumer just they bought installs it in system that's all. One should know the features and options available in the Security software's.