When I had D3 it had keyless entry and start, 1st push on the button turned on ignition, wait for glowplug light to go out, 2nd push started engine. Never used the key in barrell so don't know about that. If the switch is dodgy with not a very good connection it could register single push as multiple pushes and start engine straight away but that does not explain why it would do the same with the key. I also did not have to press brakes to start.