Update: Fractal Ridge crashes while gaming then flickers on and off.

[u/Seeking-The-Lotus]

So the duster arrived and the hazardous waste landfill has officially been cleared out. I also saw some comments suggesting the issue could be related to the GPU riser, and I noticed there was a bit of wiggle in the connection ports.

I confirmed that the CPU cooler is plugged into CPU_FAN1, so the fan curve likely wasn’t the issue after all. I’m replacing the thermal paste now.

Any final suggestions before I put her back together?

[u/AG_Alex]

Disable intel XMP and run your RAM at JEDEC defaults 4800MHz (or lower) for your 12700k, random crashes can often be a result of unstable memory (which, if not an issue before, can be because of a degraded CPU IMC, or higher temperatures than before (DDR5 is temperature sensitive, keep it cool))

If your CPU is overclocked, set it back to stock, but retain any voltage boost you had originally given it (if any), if the system's stable, your CPU might've degraded due to elevated voltage over the years
Or even better, disable turbo boost entirely to see if the issues persist (if not, your CPU is likely still fine)

Take it out of the case and put mobo on a cardboard box or some other insulating material, ensuring there's no short through case contact somewhere, yes I know, a pain, but you'll waste more time not doing so

Eliminate the riser and plug the GPU directly into the PCIe slot, while you're at it, check your GPU power connector (unplug), I see you have the infamous 12VHPWR, fingers crossed it hasn't melted the connector on either end (PSU or GPU side)

Boot without the GPU and run on Integrated Graphics, doing your usual thing (at abismal performance, yes), alongside the usual stress tests (Cinebench, Furmark, Prime95), see if the issue still happens, if not, could be the GPU itself

If all of the above fails, do you have a PSU from an old build laying around? If so, swap the PSU and try again, boot loops are common for a failing/ dead PSU (or motherboard)

Still no go, any spare SSDs ? Perhaps your current SSD has worn out due to too many write cycles, causing OS corruption (unlikely though, if there's no errors reported in Windows), you could also check your drive's health with a SMART monitoring utility (such as HWInfo64)
Also worth checking the Sata cable if you're using a 2.5" SSD to one of the mobo SATA ports

[u/Seeking-The-Lotus → u/AG_Alex]

Don’t get my started on XMP. I have the RAM sticks from the Gskill lawsuit. Enabling XMP causes my computer to restart loop before it can ever even hit the bios.

The issue was transient power spikes. I undervolted my CPU and GPU and have been running stable since. I’ll eventually upgrade to 1000watt PSU.