E Class 280D- HELP faulty ignition / key fob ?

[WVCHEM]

Hi guys

My E class Elegance 2010, 280D , just serviced , no fault codes , fob batteries changed. Battery v good.

FAULT intermittent starting, the noise is a click or silent , will not turn engine .

Have to swap keys , mileage is 2800 only, could this be electronic EIS fault or something else ?

Any ideas please ...