Ive noticed that lately when i put my truck in reverse I have to play with it a few times before it engages.. I first noticed something wasnt right when i was backing up and the back up sensors didnt come on..
05 Lariat w/ center console shifter.

 

Bump. Anyone??

 

Sounds like the shifter cable is worn out or out of adjustment. It could also be the pringle switch ( Black box on side of transmision that tells the computer what gear the vehicle has been shifted into.) I just had a similar issure with an E450 and replaced the pringle switch and adjusted the gear shift cable and no more issue.