Summarize:

Search for it in the Search bar, located near the bottom right corner of your screen. Fast startup is a new Windows 10 feature, which speeds up the startup time on your computer.
Open Control Panel. Click on "Power Options"  Click on "Choose what the power buttons do"  Click on "Change settings that are currently unavailable"  Next scroll down to the Shutdown settings screen and check the "Turn on fast startup" option  Now click on Save Changes