This was another vehicle but I had a similar spas out happen in my Silverado.
It was preceded by a "battery not charging" message in the info center so I should have known alternator in the first place.
anyway later on in the drive all the sudden all the guages would start flashing on and off, and the guages would jump up and down as the alternator worked in spurts. And then it all died completely.
If you look at your battery guage, does the needle sit a little lower than it usually does? Mine usually sits at 14volt, but at the time this was happening it was sitting at 12.
I don't know if 98's had a message center, but in the absence of one it could possibly throw a check engine light instead.
It could be a lot of things, but alternator jumps to mind from what my truck did.