Suddenly shutdown(toshiba M300)

Either the intake ports are clogged due to long use...how old is it? The ports need to be cleaned, must take apart machine to blow with compressed air. Take to a professioal if you are not good at DIY repairs. There are tons of parts, it can be done but requires that you are careful. Other possible soultions are a faulty AC adapter, bad memory, bad drive. There is free software availble from miscrosoft to test memory, free software to test the hard drive for bad sectors. Try those first. Change the power meter in your control panel to always show the power meter i your task bar. If you see if fluctuate from AC to battery power, then you have a problem with the AC adapter or you battery. Good luck, more than likely, just dirty ports but that is the most expensive and hated problem.

Laptops are notorious for thermal problems. Games are graphic intensive which creates alot of heat because the cpu & graphics card are both being pushed. If the fan is not adequate or the laptops vent[s] are not free then the internal thermal control on the cpu shuts down the system rather than frying the cpu. This is what this problem sounds like. You could try upgrading to a better fan or invest in a laptop cooler. Hope this helps & please remember to rate my answer.