Did your device have the April software update some time before your S23 Ultra turned off
@gulliverxc, and did your clear the cache afterwards?. My advice to you is that this issue is unlikely to happen to your device again, especially if you reboot it regularly (at least once a week) to keep everything running smoothly. I would also ensure that all your apps are up to date also. I know it will take time for you to have full confidence in your device again after this glitch, but I honestly believe you shouldn't have any repeats of this issue. Fingers crossed.