Question PC boot loops, fixed temporarily by making hardware change

[exitcode]

After coming back from a 2 week holiday, when I turned on my PC I found that it boot looped without the fans spinning down and too quickly to get into bios but after displaying the post screen for a second. After trying lots of different things I could boot once by making different hardware changes like changing the slots of the ram or unplugging all the sata drives and their power or resetting the cmos but each of these would only allow me to boot once - as soon as I rebooted it would go back into the boot loop.

1. I have tried using another single stick of lower frequency memory I know to work - still boot loops.
2. I have tried a different PSU plugged in only to the CPU and motherboard - still boot loops.
3. I have tried a CMOS reset and unplugging all drives to no avail.

Even odder is that when I do successfully boot after making a hardware change, the cpu is underclocked at 2ghz and with a voltage of 0.976V. It displays this both in the bios and in windows even when I set voltage and clock speed manually to 3,5ghz and 1.2V. Nothing has helped change this. Here is a screenshot of hwmonitor and task manager when running furmark:

Specs:
CPU: FX 6300 3.5ghz
Mobo: MSI 970a-g43
RAM: G skill ripjaw X 2133Mhz 4gb x 2
CPU fan: hyper 212 evo
GPU: Nvidia 1060 zotac mini 6GB
PSU: antec 750w truepower gold

Anyway, would appreciate your suggestions. I'm gonna try reinstalling windows and a different cpu to see if that helps.

Thanks in advance

 

[JQB45]

Do you have a spare PSU to test with? Typically when I have seen boot loops like this they have been because the PSU is dead and needs replaced. What is odd to me is you can sometimes get a successful boot, which makes it more difficult for me to say for certain its the PSU.

 

[exitcode]

Do you have a spare PSU to test with? Typically when I have seen boot loops like this they have been because the PSU is dead and needs replaced. What is odd to me is you can sometimes get a successful boot, which makes it more difficult for me to say for certain its the PSU.

I have already tried a different PSU I know to work and it still boot looped unfortunately.

 

[exitcode]

Just tried my CPU in a different computer and it worked fine with the right clock speeds and voltages. Tried a different CPU (same model) in my computer with several different sticks of ram in different slots and it once again boot looped and showed the weird 2ghz clock problem. I'm thinking motherboard then unless its some weird bios or firmware problem? I'm going to try reinstalling windows anyway probably but no idea why that would fix it if it still boot loops with no drives plugged in.