The issue you are experiencing could be related to the USB ODD directly. Our recommendation is testing with a different device to narrow the issue. The optical drive will be recognized as an USB device by the motherboard BIOS.
I don't have an alternative device except for an IDE ODD and the motherboard has no IDE header for that.
With a bootable DVD in the device it works correctly.
With the device plugged in but empty, the pause is 15 seconds - still way too slow.
Why should deciding what to boot take longer than the boot and winload itself?
Maybe the USB-HDD (multi-partitioned) is slowing things down.
I never want to boot from that, but there are no bios settings to avoid USB-HDD and still be able to access USB-ODD.
This is a stuff-up.