Why does your laptop shut down?

Answer 1

Try attaching the power cord and see if that improves matters. You probably need to get a professional analysis. My impression is that when this starts to happen, the computer has died. If you get an error before it goes, Google that to see what the internet community thinks.

Answer 2

One cause of a shutdown could be overheating. Is your laptop running excessively hot? If so try a laptop cooler stand, or working in a cool area and see if things improve. Also, place the laptop on a tabletop and not on a lap or cushion, which prevents cooling.