I got a brand new Dell Optiplex 7040 minitower from another country. I was able to play older games with it without problems such as the 1st witcher.
I replaced the videocard with a geforce gtx 1050ti 4gb to play newer games. My PSU at this time was the one that came with the pc which is 190W. This time, I can play newer games with significantly better graphics i.e. Tales of Berseria, Breath of the Wild, World of Final Fantasy. But when I try to play other games which I think is more "graphics-intensive" like witcher 2, rise of the tomb raider, total war, my pc would shut down as soon as I get control of my character. I tried opening witcher 1 again (which was previously problem-free) but my pc now shuts down too. I figured that this might be due to the fact that my PSU isn't enough for the 1050ti GPU I installed. So, I bought a corsair 450W. However, the same thing is still happening. Is this really due to insufficient power or another thing entirely?
OK now that you have abigger PSU, get a couple more fans to blow across the MB, specifically the Graphics card! Also, Set the Graphics resolution DOWN on each game to see if it plays longer. If it does (as you have not made the game so geraphic intensive), then you know it is getting hot! MORE FANS MORE FANS! They have cool LED ones now!!