No, - what Wapping said.
When you turn off the ignition it will (well, should) switch off if you do nothing or stay on if you select "cancel"
If it is ON and out of it's cradle there is a "timeout" setting which switches off the screen after a while. However the unit is still ON and quietly flattening the battery. If you want to switch it OFF you need to press and hold the on/off switch for about 5 secs after which you will be offered the choice "cancel or off" If you just press the on/off button briefly all that happens is the screen goes blank.
Have a look at "settings/display/display timeout". I choose "never". That way I know when the screen is blank, I know the thing is switched off not just resting the screen.
There is something odd goong on with mine as well. Sometimes it doesn't come on when I switch the bike on. The only solution seems to be to remove it from the mount and press and hold the on/off button for a long time. Eventually it comes to life and can be put back in the mount. This requires both hands so a straight bit of road and cruise control is needed...
Now here's a thought... if you have the timeout set to a short time, it may blank the screen before you get the "cancel or off" message
Good luck
Dave