One hint: when you turn off the bike, you will get the message something like "Do you want to turn the unit off now?" It will then count down 30 seconds before turning off. Do NOT turn it off by pressing the off button on the screen.
When I do this it turns my unit completely off - need to remove it from cradle and hold the power button in for 20 seconds or something to make it burst back into life.
If you just let it close down on its own, it will restart as soon as you turn the bike back on, or with a quick press of power button if you remove it from cradle.
(This may be a fault with my unit, as I'm sure it's not supposed to happen like that, but worth being aware in case yours does the same!)
Incidentally, while the cradle does lock the unit in place, it doesn't seem particularly secure to me. If I'm leaving the bike somewhere in public, I take the unit out and put the blanking plate in.