Im dealing with same problem now and while I have different PC specs, I have same situation.
Built my PC June 2024, played ffxiv for 8 months, took break, logging in just few times per month for some minor casual activity, and mid febraury started logging again to do pvp. Crashes start appearing approximately 25-26 feb 15-60 mins ingame.
Tried many things. Nothing helps so far. Really weird thing that I played like 15.02-25.02 without any issues and then start crashing.