2005 Jaguar S-Type rattle

You can't set the pcm or anything like that right off the bat. GM engines had the same problem on startup. What happens is there isn't any oil pressure to the bearings and they have oil there just no pressure so you hear a deep rattle when engine starts then it goes away because it gets pressure. Nothing gets hurt by it strange as it seems, but try replacing oil and filter with a filter that has a check valve to hold the oil there like Purolater, Wix, Napa, or Bosch as Purolator makes Bosch filters. A check valve looks like rubber around the little holes in the filter. That may cure it. Of course you can always have a local pro listen to the noise to get a better opinion.