So interesting flurry of tests I've had to do over the past few days due to lots more crashes, and I even managed to grab a pic at the point of crash.
Interesting to note that I did just apply a Windows Update before seeing all the crashes, which probably disrupted something about my IGPU state or so.
I think I'm homing in on the main issue though as it's been more stable after verifying my Integrated GPU status among some other things, I'll walk you through it:
Apex started doing the weird thing again where the graphics would go all fuzzy and my PC would restart a few seconds later, costing me valuable match time and RP (if I'm not able to rejoin in time).
I had a go at disabling XRP for my RAM which didn't help at all and actually made it more frequent, so I switched it back on again.
I then updated my BIOS to the latest version, just in case something weird was going on there.
I reinstalled Apex, and updated once the new Season came out, but it was still crashing (about the time I was able to grab the pic of it).
With the crashes still happening, I looked again in Apex's Crashpad folder (last crash on 10th August) and thought harder about the vague error message it gave;
ERROR_CODE: (NTSTATUS) 0xc0000005 - The instruction at 0x%p referenced memory at 0x%p. The memory could not be %s.
Apart from it being a general memory reference issue, the key here was the NTSTATUS part, relating to some function of Intel's HD Integrated Graphics Driver stuff after some quick Googling:
https://forums.techguy.org/threads/error_code-ntstatus-0xc0000005.1262544/
I went ahead and downloaded the latest Intel HD Graphics Driver, and was able to install only after going back into my BIOS and specifically Enabling Intel HD Graphics (by default it was set to "Auto").
The game has been very stable since and I've been able to enjoy some great Kings Canyon matches on Ranked for a good few hours each time.
My feeling is that Apex is still somehow trying to send instructions to all graphics cards detected on the system, one of which being the Integrated graphics (even if there's a physical GPU there, I'm still using the RTX 3090). If IGPU is Disabled or on Auto in the BIOS, I think it doesn't manage to completely switch over in time, which is causing the crashes.
Hope the Apex Devs are able to sort out all these crashes in general though cause there's loads of forum posts about it, but hopefully I've touched on something here that will help them verify their GPU code.
Again, this only happens with Apex Legends. I can run any other game fine on my PC, it's just Apex that crashes.