Win 11 24H2 can not reboot... but can boot?

If I use Windows Button -> Power -> Reboot, Windows 11 reboots and afterwards (not at the "Restarting" screen, but the boot logo) hangs on the rotating loading circle indefinitely.

If I shut down and start up again, it works perfectly fine. If I hold the power button during the infinite loading circle, it shuts down and then boots up perfectly fine, too.

Event manager has an entry about not shutting down cleanly after force-shutdown by power button, but no error messages about what caused it to hang.

Any ideas where to look? This used to work normally until about 2 weeks ago, then suddenly showed this behavior.

Both sfc /scannow and dism /online /cleanup-image /restorehealth (and /scanhealth) show no issues at all. Neither does scanning the system drive.