The fast startup mode saves the state of the system at each shutdown and allow you to restart your Windows 8/8.1 tablet, PC or laptop faster. But in return, you won't have access to the following features at startup:
Access to the BIOS
Access to the boot menu
Start Windows in Safe Mode
If you need to disable the fast startup feature of Windows 8.1, follow the below procedure:
Press Windows + X and from the menu displayed, select "Power Options".
Click on "Choose what the power buttons do".
Click on "Change settings that are currently unavailable", to unlock the "greyed out" options
In the "Shutdown" section, uncheck "Turn on fast startup".