Rattle or Rubbing??

Hey guys, I have a 1991 xj with a 3.5" lift and have developed some weird rattle/rubbing sounds. The sound is very comparable to when I turn my wheels too tight and the knobs on the tires rub the LCAs. BUT, the sound happens when the wheel is straight so its not the tires rubbing. It also only does it when you first get in the jeep and begin driving. It only lasts a few seconds, and won't do it at stoplights. You have to be away front the jeep for a few minutes. I'm lost. I've only had the jeep for 2 months so I'm not sure of the maintenance history. Any help would be appreciated,
Brett

Update! The rattle happens whenever the A/C engages. Again the rattle only happens after the jeep is started and lasts maybe 2 seconds. It doesn't matter if the jeep is moving or not. Anyone have any ideas as to the culprit?

Bdenglund