1999 Jaguar XJ8 sluggish start

I've been getting a sluggish start with my XJ8. It usually fires right up on the first turn of the key, but the last couple of days I've had to try a couple of times. Most times it will start on the first turn but, it acts like it doesn't want to. I recently changed the oil and there's been a cold snap in the weather here this last week but Ican't think of any other anomalies.