Start Up Problems in Cold

I just bought a 1998 XJ8 with about 70K miles on it. It is just a beautiful car, actually my dream car, and the mechanic during pre-purchase inspection said it had been excellently maintained. But lately, as the season has changed and it has become colder- the engine takes some time to turn over. I have heard this is a common problem with Jaguars? Is that correct? And what is the reason for that? What should I do? I changed the battery and am assuming a tune up would help? Lastly, is there a website available that identifies these types of common problems with this model? Thanks.