sudden laptop shutdown

I have an HP Probook 4525s and after I changed mobo it started shutting down spontaneously during certain actions. It usually shuts down after 5 minutes of playing a video game or during harddrive check and memory check. When browsing the internet the laptop is stable.

The shutdown goes like this: screen blacks out, power button and power cord led (white light) are blinking,, then after approximately 15 seconds the laptop shut downs completely (no lights, fan stops spinning,..).

May it be a sign of overheating?

thanks for any help here