Every time I turn on my laptop (from a completely off state) the Bluetooth is on by default. How can I prevent it from turning on at startup and then only turn it on (manually) when I want to connect any Bluetooth devices like mouse and keyboard?
If you're still looking for solutions to this, you could try this Terminal command:
sudo defaults write /Library/Preferences/com.apple.Bluetooth.plist ControllerPowerState 0
Source: Apple Support Communities thread