Sometimes it's timing ... try tapping it repeatedly after restart.
Also some "quick boot" utilities like MSI fast boot may not give you enough time to hit delete or F8 (safe mode).
Can also try pulling SATA cable from boot device, can't boot if it can't find OS files.
Have you tried resetting CMOS ?
There are other options for different MoBos but if it says "Hit DELETE to enter BIOS" right on the screen, you have obviously got the right one.