P38 diesel cutting out on tick over

hi can anyone help me? i have a 2.5 DSE P38 automatic. it runs absolutely fine except when ticking over in gear it cuts out every 10 or 15 seconds if its not in gear it tries to cut out but only for a millisecond and usually picks up again. if you keep the engine on around 1100 rpm you have no problem what so ever. this problem makes driving very difficult at junctions and roundabouts. i would appreciate any advice many thanks. pete

That all B a Range Rover then