Hello and welcome to the forum!
I don't see any evidence of BSODs in the System log, though, like you, I do see the 'dump file creation failed' messages. In order for dumps to be written all of the following must be true...
- The page file must be on the same drive as your operating system
- Set page file to "system managed"
- Set system crash/recovery options to "Automatic memory dump"
- Windows Error Reporting (WER) system service should be set to MANUAL
- User account control must be running
In addition, the following can prevent dumps being saved...
- Sometimes SSD drives with older firmware do not create dumps (update firmware)
- Cleaner applications like Ccleaner delete dump files, so don't run them until you are fixed
- Bad RAM may prevent the data from being saved and written to a file on reboot, so if all else fails test your RAM.
It's possible that some live kernel dumps may have been written. Please look in the folder C:\Windows\LiveKernelDumps, under there may be several sub-folders. Look in all sub-folders and upload and dump files you find. Do you have two Windows drives in there?
One of the things I note from your msinfo32 output is that there seem to be two drives with the Windows partition structure on; the two 1TB 980 PRO NVMe drives? Two active Windows drives can cause lots of strange issues.
Regarding the HWMonitor data, that's a lot of numbers to trawl through and it's hard to get a full picture from the data in that form. It doesn't appear to be overheating however, although your CPU temps increase towards the crash they're not worrying at all. RAM and GPU temps are fine too. There's no point in my looking at the voltages, hardware isn't my area of expertise.
Due to the lack of BSODs and that neither your System log nor your Application logs contain any failure error messages that might account for these crashes, I think that these crashes most likely have a hardware cause. The hardware just fails underneath Windows giving it no opportunity to either log the error, attempt any recovery, or BSOD.
RAM is always the first port of call when we're looking at hardware problems. I see that you have run Memtest86 but even that's not perfect, it can't find every possible RAM problem. It seems to crash several times a day so I wonder whether you might try removing one of you four RAM sticks for a couple of days? If you rotate through the sticks so that each one is out for a couple of days you' should be able to determine for certain whether one of them is flaky.
If it was working OK and now it's not then for sure something has changed. I see you say you don't know what changed but it wouild help a great deal if you could think about what might have changed. Have you moved the PC? Bumped it? Dusted the outside even? Have you had any changes external to the PC, like a new fridge or TV, a power outage, even a new smartphone?
Since the problem happens most when gaming, you might try removing and reseating the graphics card. It's also worth removing and reseasting all the M.2 drives. It seems that the M.2 slot design can be a little flaky, I've seen many niggly issues that were solved by reseating an M.2 drive.
You could also try
starting Windows in Safe Mode. You won't like it at all however, because you won't be able to do any useful work. Safe Mode loads a stripped-down version of Windows, with only critical services and drivers loaded. Typically no third-party drivers are loaded, so many devices won't work properly (or at all) and your display will be low res because you'll be using only the Windows basic display driver. The whole point of Safe Mode is to give you the most stable Windows platform possible, if it fails in Safe Mode then it's definitely a hardware cause.
Please let me know whether those two 980 PRO drives both have a Windows system installed.
