|Wish I had.|
I rather doubt it is BIOS unless you have some weird hardware fault. No harm cleaning the RAM edge connectors with a pencil eraser as they can sometimes play up, although slow boot would be an unusual symptom.
Usually it is "something" hogging the show during startup - computer suppliers goodies are frequent causes. Clutching at more straws, have you only one AV running in the background, and is it any better with the AV temporarily disabled?
Always pop back and let us know the outcome - thanks