“Just to confirm, even thought when I double click avast and it didn’t appear but after I restart the pc it appear it is nothing serious?”
It’s nothing serious. It could be a computer or avast problem i.e. windows security center and avast miscommunication. If I were you I definitely going to uninstall avast 8 via add/remove, run avast uninstall utility in safe mode to delete all avast files and programs, and install Avast 2014. So all the issues and problems will be cleared up.
“So for future references if in the task manager it shows that avast is running it means that nothing is wrong with avast? Is there any symptom I should be aware of just in case?”
No there is no symptoms to worry about, you are protected by avast".