After not having any issues with my current installation, my computer now just reboots after a few seconds after logging into KDE. (Been using ONLY arch for 2+ years and this installation is about a year old by now. Windows never touched this computer.)
It's considerably slower on the login screen already, and takes a while to finish loading the desktop. After that, it doesn't take long for the screen to go black and the whole system to reboot, getting into this loop.

For reference, my system is
CPU: Ryzen 5 5600
GPU: 7700xt
RAM: 2x16gb DDR4
Motherboard: B550M PRO-VDH WIFI (MS-7C95)

Of course, I took some pictures of the error that comes up after reboot and it basically reads as follows:

[Hardware error]: System Fatal Error
[Hardware error]: CPU :4 (19:21:0) MC5_STATUS [...]
[Hardware error]: Error Addr:0x01ffffffc05d33b2
[Hardware error]: IPID:0x000500b00[...], Syndrome: 0x000000004
[Hardware error]: Execution Unit Ext. Error Code: 0
[Hardware error]: cache level: RESV, tx: GEN, mem-tx: GEN

Not writing everything down (as noted by my use of [...]), but that's the gist of it (the values and numbers may vary slightly). Of course, after some research I noticed that the problem matches the description of https://wiki.archlinux.org/title/Ryzen#Random_reboots, so I started taking some measures to troubleshoot it, given that I never messed with these things (been running it stock ever since I built this PC). First things first, I updated my BIOS. Then I Tried to change my curve optimizer with an offset of +4, as suggested in the wiki. Nothing changed. Then I Went onto section 4.2, which still matched what is happening to me, and applied PBO+4 or +6. Nothing changed. Then I Came here to the forums, and checked some threads from people that had the same or similar issue and saw some suggestions to also slightly underclock the CPU by -50. Nothing changed.

Might also be good to note that before I tried messing with all that, I also tried to boot into the arch ISO without any success. Also, for good measure, tried doing the same but with linux mint's and nothing worked still. So yeah, I'm pretty much completely locked out of my main system and don't really know what to do right now other than ask here.

If it helps, last I updated my computer was on the 4th of this month.