Please help have a look at the hardware issue on my iphone 4S

My iphone 4S always shutdown itself in every several hours, then I can only reset by both power on/off and main buttons. Sometimes it even cannot be reset by those buttons, I can only connect it with itunes and itunes prompt a dialog to say your iphone need restore. Now I cannot afford to restore it several times in one day, I almost cannot use my iphone 4S. I just found there are some crash report in iphone 4S diagnostics. Could someone help clarify why this will happen?