I have an issue with my 2000 xj8. I turn the key and the starter spins but does not engage the flywheel to spin the engine. Do I need a new starter? Could it be a simple thing? I had no problem with it before.

 

It sounds as though the starter solenoid is not pulling and engaging the flywheel. The most likely is you will need a new starter. You can remove the existing one and determine if the solenoid mechanism is damaged, corroded or just plain shot.
The only other possibility would be missing teeht on the flywheel ring gear. Since you haven't had a history of starter engaging problems I would go for a new starter.
At a cost of around $400.00 I would search for a local rebuilding company for the one you have.

 

Long, long time ago, there used to be a guy out by Kraft Chevrolet out west of the city that rebuilt alternators and starters.

 

I had to plant my face firmly into my palm on this on. I couldn't see if the engine was actually turning when I tried to start the engine so I put a mark on the fan to see if it moved. Due to the sound and the fact the mark did not move seemed to indicate a starter problem. Later that night in bed I remembered it had an electric fan. Long story short, the starter works fine. I had washed the oil off the cylinders and there was no compression. Put oil down the spark plug holes and it stated up.

 

Bore wash strikes again. Glad it worked out and appreciate keeping us informed.

 

Good for you, cheaper and finally easier than a new starter.

Yeah, seems a winter problem.
Maybe temperature related, extra fuel injected by the ECU?
Perhaps that's the final nail to the coffin?