I have just purchased a 2017 Jaguar XF R sport and have noticed this noise too, usually at lower speeds and it sounds like a tappit rattle that you used to hear on older cars. It's not unduly loud but it is there and a tad annoying. I am glad people have identified what this is as the car is under 2 year Jaguar warranty. Does it get worse if you do nothing about it or is it needing to be repaired?
Grant.