I tried a lot opportunities . Firsty wrote new windows. But problem still was. Latter change thermal compound. But problem still was. So tried other things , tried take out battery and without battery just with power cable. Again computer just turn off after 30min. And couple tested just in bios mode after 31minutes laptop just shutdown. So what kind of problem is ?? Thanks for solution!
Your laptop seems like overheating itself and the outcome would be it will shut down by itself. All PC has this certain feature where when it hit a certain degree or heat it will shut down by itself. Since you already have changed the thermal paste in it and that normally should fix the problem, try using a Laptop Dock where it will have set of fans under the dock that should help to cool down your laptop. Another step you might want to do it to clean the laptop again from debris that might be hindering that fans to spin to it's full potential.