I have a 2003 X350 4.2 V8 XJ. It has done 99,000 miles. When starting from cold, the engine emits a rattle, briefly. Seems to be from the top of the engine, and lasts for only a second or two. It would appear to be caused by a shortage of oil, because having run for even a short time, on next start-up it is perfectly ok. Any experiences of this? Any suggestions for cure?