1997 Jaguar XJ6 Check Engine Light

The Check Engine red warning light suddenly came on in my '97 Jag XJ6 the other day for no apparent reason. Owners manual just says bring to dealer and dealer couldn't take the car when I could get it there. But dealer says car can be driven and not likely to have a break down on road unless the light begins to flash. Car is well maintained and seviced five months ago. Seems to run fine; only thing that seemed irregular was a few weeks ago, had some hesitation(like bad gas?) That has subsided? Any urgency to bring car in --or refrain from driving it? Thank you.