PC boots in low resolution

I recently upgraded my GPU from a ROG STRIX 2080TI to a Gigabyte RTX 5080 Aero. Ever since, my PC boots in low resolution, and only switches back to normal after a minute or so after booting it.

System:
- Z390-E Strix
- i9-9900k
- RTX 5080

- Windows is in UEFI
- CMS disabled
- My monitor is plugged in via DP (to GPU, closest to motherboard)

What i tried:
- Clean BIOS update
- Reinstalled Nvidia drivers with DDU (twice)
- Disabled Fast Startup

I didn't have this issue with my old 2080TI
Any idea why the resolution delay happens on boot with the new card?

Thanks in advance :)