My XJ8 worked flawlessly since birth (1998).
It always had a very light cluck-cluck sound
under the gearshift, sometimes audible when
rolling on rough road.
This very very light clucking (like the tapping
of a spoon by a 3 month baby on an egg shell ;-), or like a dull click
of computer mouse becomes more frequent
since a few weeks.
Anything worrying ?