Mechanically, the biggest problem
AFAIK: the cylinder walls of the V8 engine were treated with Nikasil that wore off, requiring a rebuild of the engine. However, the problem was cured by 2001 or so. A car may be affected if it has six digits in the VIN# at the end. If it's got five digits, the engine has steel liners instead.
According to some sources, the problem was not the Nikasil coating, but rather too many cold starts in sequence, leading to gasoline washing away the protective oil film on the inside of the cylinder walls.
Other problems, the upper cam chain tensioners break. Jag later replaced them with metal ones. It's unclear exactly when they did so, and the only way to find out what material is used in the engine of a particular car, is to physically check. If they are not metal, it's recommended to immediately replace them.
The water pump is a weak spot. Earlier versions didn't have a frots plug. If the pump does, its fine, if it doesn't - replace it.
If you want to go more in depth you'll find a lot of stuff about these well known problems via Google.
Good luck. That gen Jag is certainly still good looking, low four door cars.