My PC is acting weird and keeps turning off

For some reason, my Dell Dimension 3000 is acting VERY buggy ever since I tried to replace the CMOS battery(btw I confirmed it isn't the battery)

• The PC keeps automatically turning off, most of the time staying on for less than a second.
• If the PC manages to get on for a decent amount of time, I might see a error such as "Previous startup attempt failed at checkpoint [random every time]" or "Previous startup attempt failed due to thermal event"
• Speaking of the thermal events, one time I saw that error, opened up the PC and found out the CPU was stone cold.
• Sometimes it shows me a glitched out screen(the pc uses integrated graphics)

Here are pictures of the internals:

And my ports:

• AC power cord
• VGA cable(integrated graphics)
• Keyboard and mouse(High-speed USB ports)

UPDATE #1: I tried turning it on and it succeded:

• Here's a picture of the error screen(I had unplugged the usb keyboard and mouse for troubleshooting purposes)

• The screen glitched out right after the error screen and then shut down:

• I tried a few more startup attempts and now it's essentially thermal events(CPU is still cold)

UPDATE #2:

• The issue went away! Hopefully it stays that way. I'll have to see.

UPDATE #3:

• It's back and worse than ever! First time I booted it up, it showed me only an amber light. All diagnostic lights off, no video output, and no beep codes.

• The regular issue came back after that.
• I suspect the PC may only work after it warms up.