This may be HW specific issue because it’s happening to me and my college. We have both new laptop Dell Precision 3561 with updated openSUSE Leap 15.3.
Not always but every few day after standard shutdown the laptop is not able to boot. Boot sequence starts normally but at the end it suddenly shutdown itself via systemd-shutdown. Moreover this boot is not recorder in journalctl --boots. I am only able to take a picture with my phone.
Eventually I am able to boot after many tries. Not sure what actually help. I did try old kernel, recovery mode, booting into multi-user runlevel, nomodeset, by switching between prime-select intel/nvidia a by pluging and unplugging display cables.
The system has Secure Boot On and has encrypted filesystem.
BIOS is up-to-date acording to dmidecode (Version: 1.6.0). I did update it from Windows on the first day when I got the laptop. Which answers the second question, I have dual-boot with Windows.
I had a theory it is caused by secure boot and missing signature from nvidia kernel module after an update of kernel or nvidia drivers, and/or secure boot configuration in BIOS, but I am less and less sure about that.