first of all never keep the phone on auto-update..let it do manually..!!
Secondly connect your cell to the computer through USB..and scan the whole drive with pc's antivirus..if it shows any virus or malfunctions then heal or remove it permanently..you can do this by manually installing any anti-virus in your phone too..
Then after scanning the issue enter in your content on drive through PC..try and remove all the unnecessary files which you dont need etc....make sure you have delted the files which are duplicated or unnecessary for you..
Auto-update option should be disabled this may cause problems for you unknowingly..
After doing all this switch off your cell and restart it again in 10 minutes..
Make use of apps like app2sd pro , anit-virus , android booster , mobo task killer for cleaning you caches etc. and even reboot pro..
All the above prescribed apps are top class which will help you keep your mobile clean and safe...
By use of app2sd make sure all the apps moveable are moved to SD card..!! because many a times you have to manually move it to SD..!!
Try this might help you..!!
