If you have a dual-boot setup, this is perfectly normal. The computer simply wants to know which operating system to use.
If you don't have dual-boot, then we can turn that off (the choice will be automatic since there is only 1 to pick from).
Hit the following combination on your keyboard: Windows Key
and hit Enter.
Navigate to the Advanced
tab > Startup and Recovery
the box that says Time to display list of operating systems
(mine is checked now):
Feel free to reboot and make sure the boot manager doesn't rear its ugly head again.