New X505-893 and big problem

I just got mine laptop today finally but i'm getting problems... Whenever I play games sometimes there is random lock ups, like the laptop would just randomly be stuck and not respond anymore so I have to restart laptop. This also happen when I was watching video and had a lot of other things running in back ground. Note, I JUST GOT THIS laptop, not eve 24 hr yet and no O/C of any kind. How can I go about finding what kind of lock up this is or do I need RMA?