2002, 540i Won't start, intermittent...
 

My 540 6MT sometimes doesn't start. Turn off key, turn back, still no turn over. Then,
3rd or 4th time, turns right over. go two weeks, starts fine, then one day, same no start, try again, and it starts.

It feels like a dead battery but would the battery quickly come back to life?

Any help appreciated. Thanks.

I'd go for ignition barrel or clutch pedal switch. Car will not turn over unless you have the pedal down, fault switch could cause it to believe clutch is not down.

I would start by pulling the codes.

i think you have a short on your positive battery cable. next time that happens tap/shake the battery cable and it will work.