Got in my car yesterday, put the key  in the ignition and turned it, all normal dashboard lights  came up, but when turned to start the engine, all power vanished? 
All lights went off on the dashboard, car wouldn't start, no radio, windows or anything. wouldn't even lock with the central locking using the key. had absolutely nothing. kept  putting the key in and trying to start but  no power whatsoever.
Spent about half  an hour looking over everything, found no obvious fault, then power randomly came back? 
The clocks and trip  counters on the display  had reset, it had also reset all the milage and mpg of my set 2 on the hud? 
Radio had reset to default radio stations, mixer  settings etc? 
Car  has run fine since but am concerned as to what may cause this? Has anyone else had a similiar problem/know what it may be?
Cheers.  
