One trip it is working fine,radio and gage lights all work and then for no apparent reason,the system will go dead and when l come back to the car the clock radio has defaulted to 12:00 and no stations and last night l thought l was stuck when nothing would work .Turning the key did nothing,like there was not even a battery in the car.Then the power came back on and the car started right up.

Sounds like you've either a loose or frayed wire or corroded wire or a rusty electrical system connection or even a burnt or melted wire.
First of I'd be checking the battery terminal connections to make sure their tight & clean keeping in mind that most electrical failers in vehicles r grounds.Then check the starter,alternator connections , plus open the under the hood fuse box & have a look at each fuse & relay making sure they r in solid & also try popping each fuse & relay out one by one check to see if any of the pins on them r corroded etc , plus I'd be checking the engine block ground too.It may end up a bad ignition or ignition related faulty wire.
See bec ur vehicle is a 97 I'd be cleaning all of the contacts & connectors or connections I've mentioned by using a set of small wire brushes, small file & fine sandpaper.Plus I'd be checking the in car fuse panel too for bad connections or faulty grounds etc, also be changing & using new assorted proper o-ring connectors & battery terminal connectors.

Hope that helps & best of luck.By the way I'd be sure to clean all the fuses & relays one at a time , plus keep in mind that it does sound like a main lead positive or negative wire or connection is at fault here & also a wire could be so badly corroded in side that it can cause these types of electrical failers too.

l think your problem is so easy to resolve that im scare to tell you what is it.

something call

ROOM FUSE on the kick panel O_o
i hope to be wrong