My engine just quit- I have a 2006 RV using a Ford E450 frame with a V10

Hello, I believe you have a bad ignition switch, but I use the term loosely. Since no dash lights are coming on, it seems like the ignition switch is losing electrical contact in the ON position, which would be why establishing new contact works. Try turning it on in the driveway and jiggling the key. See if you can get it to turn off without turning the key. Once it turns off, check for continuity across the switch by testing at the base of the steering column where the wiring loom sticks out of the trim panel.