I have a XJ6 TDVi 0n a 2056 plate.
Recently on morning start the seat doesn't auto re-set and the radio sometimes doesn't work!!
Turn off and re-start all is OK.
Could this be an early sign of battery failure?

Thanks for any advice

 

Faults and alarms that come up after a cold start, but don't come up again after a soonish restart after a short run can certainly be a symptom of a failing battery. The 350's electronics are notorious for being sensitive to even mildly low voltage.