Q: Bluetooth not working on start up 10.11.4 15E65

Hi there Alistair,

It sounds like bluetooth isnt working initially on your computer when you turn it on until you plug in a USB keyboard and mouse and restart it. I would reset your SMC then your PRAM in that order:

Reset the System Management Controller (SMC) on your Mac

Then:

NVRAM or PRAM

If the issue persists then I would boot to safe mode to clear some system level caches, and verify the disk as well as repair it if needed:

Try safe mode if your Mac doesn‘t finish starting up

Follow these steps to start up into safe mode.

1. Start or restart your Mac. 
2. Immediately after you hear the startup sound, press and hold the Shift key.
3. Release the Shift key when you see the Apple logo appear on the screen.

After the Apple logo appears, it might take longer than usual to reach the login screen or your desktop. This is because your Mac performs a directory check of your startup disk as part of safe mode.

To leave safe mode, restart your computer without pressing any keys during startup.

Once you log into safe mode restart as normal and test it all out again. Thank you for using Apple Support Communities, all the best!