I have a 01 XJ that all of a sudden it decided not to start. When I put the key in and turn it to run everything works until the moment I try to start it, I lose all power like the key is not in at all. I have to smack the steering column to get power back. I checked the battery and it's connections and they are good, I'm lost at this point please help

 

I think that's telling you were the problem is located.
The ignition switch is in there and it, along with it's connector is a common failure.

 

Times two. If you can "jiggle" something and it works, you found it!