Don't be concerned about this, it is just something that happens when the car gets it's nickers in a twist. I don't think it's even really a key related thing. When I've had it come up, it's been when I've stalled the car. (I know - it happens!) 9/10 times, the car just starts itself, but, occasionally, it will lose it's way and show the start manually message.
Obviously, if it becomes frequent, you will need to get it looked at, but, until then, don't worry about it!
