problem starting jaguar x-type 2.0 sport diesel?

Car never fails to start first thing in the morning,but subsequent attempts to start results in engine coughing and spluttering. Have to turn off the ignition and try again and eventually after 3/4 attempts engine usually fires ok. No problems other than starting. This problem initially occured some 9 months ago and then cleared until recently and is now occuring all the time.Just tried adding injector cleaner to petrol,but no change yet. Anybody got any ideas please ?