Dead, Dead, Dead, then after 10 minutes FINE!?!
 

This has happened twice now. The first about 3 weeks ago, the second, today.

1) I remote unlock the door.
2) Insert key in ignition, and begin to turn and, DEAD! No dash lights at all, no dome lights, nothing! I open and close the door, and the auto window down/up thing does not work so the door is stuck open a little.
3) Key out and in and still dead. Try to start multiple times, nothing. Behaves as if the battery has been removed.
4) I leave to find jumper cables. Return and open the door and I notice the DOME LIGHT comes ON when I get in!!
5) I insert the key and it STARTS RIGHT UP!!

Who knows what this might be? I don't see how it could be a weak battery because it dies so hard then comes back to life only 10 minutes later. Is there some kind of fault detection that will cause the car to behave like this? I checked for codes and there are none. Nothing at all unusual other than this!

You might need a new battery, Mini's start doing all kinds of weird crap when battery is going, at least on the first generation cars not sure on the R56 and on.

Same Problem - Solution
 

This same thing happened to me three weeks ago. The first time I hit the roof of the car and everything came back on, weird...The next time I had to crawl through the back and wiggle the ground cable and she came back to life so I cleaned contacts and swapped out ground cable. Worked for one day and then did it again. After further investigation, I found the Positive lead on the battery was loose. Simply cleaning contacts and tightening up fixed the problem. Been fine for the last three weeks. I guess when you try and start the car, the amount of amps needed to flow through the cable is restricted due to the loose connection and the car simply shuts down and plays dead. Kind of frustrating at the time but easy/cheap fix. Good Luck!