I brought an Optiplex 390 on eBay a few months ago It has 8gb ram, gtx 1050, and an i5 processor with the stock psu. So today I left the PC on overnight to download a game and when I came home it would turn on and turn off with the led number 3. Also, the motherboard has a solid orange color but that was on since I got the system.
Now it turn on for a few seconds with a orange power button and led 1,3
Edit: After some time I was able to press the power button and now it boot up after 1 min it shuts off. Next I replace the cpu and did the same thing I was able to get to my login screen and then it shut off after 3 min