Probably a leaking air shock or the piston seal in your air suspension compressor needs replacing; do a search on this forum and you will be resplendent with good, sound advice!
Try Don B's Air Suspension 'Sticky' as a starting point....https://www.jaguarforums.com/forum/x...ration-174819/
Also, giving forum members some information about which X350 model you own, N/A or S/C engine, year, mileage etc will help them to give you relevant advice. Put this information in your saved signature so that you do not have to keep typing it every time you post.