Notebook freezing unexpectedly !

hello,
I have a HP Pavilion 15-e001ax Notebook PC and this freezes randomly with no error messages.
I have no specific application with which it is freezing. It can freeze anytime when closing lid, watching movies, working on excel, browsing internet, playing music.. I mean literally anytime. and I have to power it off using power button and then start it again.

I called HP guys and they told me to clean temp files and folders, to increase Page File size (though I have 8GB ram) but of no use. I even refreshed my OS (windows 8) but still problem persist. I have checked every component (HDD, Processor, Ram, vRam etc.) but every test passed.

Please help me if there is anything I can do to not to face this problem in future.