Thank you for your response..
yesterday.. one of the members a (community helper) of this page replied to my problem.
and he told me to try "SAFE MODE" and so i did but still problem exist again..
-on the app games issue. No, i didnt install games except on known social media apps i updated them..
your idea on trying factory reset? yes i did that yesterday too.. it works fine in the last 2hrs.. but AGAIN the unwanted reboot occurs again. i thought it was okay because of factory reset.. to find out it happens again. till now..