1. I get the BIOS splash screen during a cold start, but I don't always get it anymore during a restart.
2. The boot sequence proceeds normally until just after I type the password. Then there is a delay from 2-20 seconds (spinning wheel) until desktop.
3. Sometimes the desktop pops right up, sometimes it seems to struggle, coming up partway. Like taskbar will be slow to pop up.. sometimes.
Once I'm "on" the desktop completely... everything seems fine.
I'm on Windows 10 at the moment. (Same problem on Win 10 and Win 11)
The 1. issue seems all too familiar. I had several strange video/display issues appear after a BIOS update, until I completely disabled CSM. It's on by default for most motherboards, and in the case of ASUS boards it remains enabled even after you turn on Secure Boot - or it does as far as the UEFI/BIOS enviroment is concerned, it would still be impossible to boot from devices without installing SB keys on them. After the BIOS update when I restored "optimized defaults" I must've forgotten to disable it again. All other settings I restored to how they were before, such as XMP and Secure Boot. As a general rule (that I can now vouch for myself) it's best to disable CSM if all of your hardware supports UEFI, it ensures that they will be operating optimally. The "emulated BIOS enviroment" is always a compromise of sorts, and not all motherboard/video card/display combinations like that.
One of the issues was the one you're having, I could only see the BIOS splash screen/OS loading circles after a cold boot, never during restarts. Another thing was that the resolution of those screens was set at 1024x768 instead of my native 1440p. And yet another thing was that after Windows restarts, the display was dimmed when I got to the desktop. Yes, dimmed, as if the display's gamma/contrast/brightness settings had been altered. No setting in Windows or with video drivers would fix it. Only power-cycling the display would fix it, including the display going to sleep mode. It was very handy during Windows feature updates, so that I could see what's happening.
The 2. and 3. issues would seem to indicate either an account or Windows installation corruption, but since it's happening to both of your disks, it's unlikely. Not impossible, but unlikely. It would then seem as if the problem is hardware. It's known that motherboard SATA or cable issues can cause OS corruption, but since everything works normally after sign-in, that can't be the case.
