Ok, so I found an answer for you and while it doesn't specifically state that this is an OEM version made specifically for whoever prebuilt this machine, it does indicate that there are different REVISIONS, and yours, for future reference, is revision 1.x. Revision 1.0 is different, and has the BIOS versions I listed above. For your version, bookmark this for future reference so you don't accidentally in the future mistake your board revision for a rev 1.0 board.
https://www.gigabyte.com/us/Motherboard/Z790-AORUS-ELITE-AX-rev-1x/support#support-dl-bios
The latest BIOS release for your board is version FH and I would advise you to update the BIOS to that version. If you are not familiar with updating the BIOS then I would highly suggest you watch ALL of these videos, twice, so that you are entirely familiar with the process, then proceed to update after downloading the BIOS release version "FH" and putting it on a FAT32 formatted flash drive. You can also update IN the BIOS using regular Q-flash instead of Q-flash Plus, but Q-flash Plus is a lot easier and far more foolproof. Just be sure to follow the directions from these videos exactly as outlined in them. There may be very minor differences between Gigabyte boards that have Q-flash plus such as different type of flash button or flash button in different location, but process is basically identical for them all.
View: https://www.youtube.com/watch?v=Mf-gXBskUGs
View: https://www.youtube.com/watch?v=7cQLYROKJ_Q
View: https://www.youtube.com/watch?v=YVHa46UoM0A
You Xilence Gaming is extremely, EXTREMELY poor quality. It is about as bad as bad can get and is listed on the Avoid tier here:
PSU Tier List will help you to choose the best PSU out of hundreds of models on the market. From budget to the highest end Power Supplies.
cultists.network
But even if it wasn't, I would already know that because aside from one very mediocre Xilence model series which is the SQ series, I have never seen a positive review of ANY Xilence power supply and have seen a BUNCH of extremely bad ones including almost every one of them stating plainly that Xilence PSUs are dumpster fire type units. I would VERY HIGHLY recommend that you replace it immediately with something that has decent quality and is either listed on Tier A or B at the link I posted above for the PSU cultists tier list or among those listed as recommended on my PSU recommendations thread here:
Below you will find MY standard list of recommended power supplies and beyond that this thread is intended as a landing place for questions or discussions regarding specific units, platforms or related PSU tech, all of which are all welcome to be discussed here. If it's related to power supplies...
forums.tomshardware.com
If and hopefully WHEN you DO decide to replace it, and there is a VERY good chance that this PSU is your entire problem (And honestly I'd probably wait to do the BIOS update until after you've replace the PSU to ensure a sketchy PSU doesn't cause any problems with the update, but I'll leave that decision up to you), it would be wise to come back here and ask regarding the specific model you intend to update to especially if it's listed on Tier B on the Cultists tier list because there ARE a few models that they have listed in positions that many of us don't 100% agree with and believe are better off avoided. Mostly it's fairly accurate, but there are, in our opinion, a few discrepancies on there. Expect to pay somewhere in the realm of 80-120 dollars US if you want to get a PSU that is worth purchasing and would be considered good enough for your configuration. Keep in mind, "watts" means nothing and "brand" means nothing. ONLY the model really matters because there are 500w models that are far better options than some 1000w models and every brand out there has both good and bad models so it pays to know exactly what model you are getting and make sure there is a trustworthy professional review of that unit before doing so.