while driving my 1999 dodge grand caravan w/ 133,500+ miles on it the dashboard lit brighter and the seat belt reminder light came on then went off and the dashboard returned to its usual glow. What could this be?

That generation of Chrysler/Dodge minivan sometimes had problems with cold solder joints in the instrument cluster.

to NYBo: is what you stated anything serious?

If a connection goes totally bad in the cluster, the vehicle can be rendered unable to start.

I concur w/NYBo that this could well be caused by a problem w/the instrument cluster. Probably best to just keep an eye on it for a while. Hopefully it was a fluke. It could be other things too, like the alternator. But more likely is the cluster or associated connector in on the fritz.