I have a 2004 5.4 with 250k miles. Engine was replaced at 174k. Once or twice a year when I try to start...nothing. As if ALL power has been disconnected. After 5 or ten minutes it starts right up but the radio and climate control have reset. Just as if battery was completely disconnected. See video of last time this happened.
Anyone know what the problem is? My mechanic is stuck.

 

Inspect all battery connections. Or you have a faulty ignition switch.