2008 xk. The heater works good when I first start the car then if I stop the car turn it off for a few minutes it only blows cold. Got any suggestions.

 

I've moved your post to the correct location.
Don't forget your intro in the new members section.

 

Check coolant level?

 

Yep 1st place to look

 

I would verify it's not in the automatic temp controls by forcing the system to full heat by setting the temp to 85` and forcing the fan to run in manual.

Might also be worth while to check for any HVAC codes with a good OBDii reader. These cars are pretty intelligent and will know when things aren't right even if they don't pop a warning on the display.