On my 97 Xk8 the headlights are not on a auto shut off system. You know, the sensor thingy. Christ, my 94 Caprice had auto turn off head lights.
Was this even an option in 97??? If not that is sad for a car of this make and COST!

 

You can tell if you have auto headlights (as well as auto wipers) by looking at the headlight stalk left of the steering wheel. There's a notch selection titled, "AUTO." The same "AUTO" is on the right stalk for the wipers.