Cannot boot into EOS normally, can only boot after booting into Windows

Hi there. I have run into a very strange problem, I have installed EOS, but I am unable to boot into it normally, when I restart my system and go to boot EOS in Grub, it takes me to a completely black screen. But, if I go to my BIOS and load into Windows, it loads for about 15 seconds, restarts automatically without a prompt, and I am then able to boot into EOS normally.

I think it may be due to the fact that I have my EFI partition on one SSD, and EOS on another, I thought that simply marking that EFI partition as the /efi/boot would work, but it is causing this issue, (I think.) I can reinstall if necessary, is the issue that I am dual-booting? If so, how should I set up the efi partition to avoid this issue? Should I just single-boot to avoid issues?

Thanks for any help!

No, that is totally fine. It doesn’t sound like an issue with the EFI partition to me from your description.

To be clear, are you saying you can’t boot into Windows either?

Well, I can, but then after 15 seconds it forces a restart without a prompt or anything, then boots into grub, then I can boot into EOS. I haven’t tried to boot into windows after it restarts. I am not sure what else would be causing it, as I have used other distros and not encountered an issue like this. I’m tempted to just nuke the windows install, as I haven’t used it in months, but I don’t want to do that in case I am left without a bootable system at all.

Tried to boot into Windows again. It boots into the desktop, restarts, and then I went into grub and tried to boot into Windows again instead of EOS, but I am now not able to, it threw up a screen to try and repair the Windows installation. Perhaps the Windows install is corrupted and that is causing the issue? Now I am really considering just nuking everything and seeing if a completely clean install fixes the issue.

make sure that fastboot is off in BIOS/UEFI and also that Fast Startup/Shutdown are off in Windows, too.
UEFI with fastboot does all kinds of reboot-persistent shennanigans, and Windows own fast startup/shutdown procedures add to that same problem.

You should also consider updating the BIOS. The version you are running is currently not available on the Gigabyte homepage, meaning it was most likely pulled for being faulty.
I had similar issues like you have now on my Asus Motherboard last year due to a faulty BIOS - could solve them temporarily by a hard BIOS reset (battery removal) but they appeared again after some weeks. Next BIOS update the issues were gone.