PC keeps turning off after being turned on

I cannot find much info on your pw supply other than some basic specs. IMO it looks like a junk unit; only 32amp on the 12V rail. Any quality 500W unit is going to have approx 40amp on the 12V rail.
Your unit appears to supply much of it's power to the 5V rail which is useless on a modern system.

You posted that you did not remove the side cover. IF you are comfortable working inside the case do the following;
1 System OFF and pw cord removed from the back of the pw supply

2 Pull the pw connectors from ALL drives; both hd and optical. If you have a M.2 type drive, remove it

3 Reseat ie remove and replace both atx and aux/cpu pw connectors on the motherboard. Be sure they are fully seated

4 Remove ALL ram and blow the slots out with a can of air. Reinstall the ram and be sure it is fully seated

5 Disconnect any usb device ie printer, hub, whatever. Leave the keyboard connected to a rear usb2 port

6 Clear cmos with the clear pins or jumper. Read your motherboard manual for detailed instructions

7 Reseat the video card. Note there is a latch that must be depressed to remove the card. Do not just yank it out; you will break something. Be sure the card is fully seated in the slot

8 Replace the pw cord and attempt to pw ON. If the system will complete POST, then shutdown and start connecting devices one at a time until you find the failed part. If the system will not POST in the above config, then you need to swap parts with known good units; ie motherboard, pw supply, ram, etc

Note if you are not comfortable working inside the case, the best advise is to take the system to a shop and have them diagnose the problem for you. By shop, I mean just that a real shop and NOT a chain store.