My PC is Stuck on BIOS Splash Screen – What Can I Do?

Hey everyone,

I'm really struggling to get my PC up and running. It keeps freezing at the BIOS splash screen and won't boot from my USB drive. Even though the keyboard lights up, pressing keys, like Caps Lock, doesn't seem to do anything, and the PC doesn't recognize the USB stick I'm using.

Here's a quick rundown of my specs:
- Motherboard: Gigabyte AB350-Gaming (BIOS version F53g)
- CPU: AMD Ryzen 7 5800X
- RAM: 16 GB (I've tried using a single stick in slot A2)
- GPU: I've tested with and without one, plus I've checked HDMI on both the GPU and motherboard.
- PSU: 650W
- Drives: Completely unplugged for now
- USB: Using a bootable Windows 10 key that wasn't created with Rufus.

I've already tried a few things:
- Resetting CMOS by removing the battery
- Minimal setup with just the CPU, one RAM stick, and either the GPU or integrated graphics
- Unplugging all drives and peripherals
- Checking PSU connections (noted that the SATA cable was in Perif1)
- Letting it run overnight, but still stuck on the BIOS screen.

I haven't attempted:
- Rebuilding the USB with Rufus
- Reflashing the BIOS (still on version F53g)
- Testing with a different PSU
- Breadboarding the setup
- Using a PS/2 keyboard since the USB ports might not be responsive beyond power.

Has anyone experienced something like this with this motherboard or CPU combo? Do you think it's a BIOS issue, a bad USB key, or something more serious?