96 caravan Misfires

My 96 caravan started misfireing  and then it clears ..and then it misfires.. if I get on the highway it clears after a mile or so.. and stays running smothe till I stop and shut it of , thought i got water in the tank but that was 2000 Miles ago ....it's old but it's My work truck

Well, the place to start is always with the basics. The most common causes of misfires are really simple things like old spark plugs & wires, fuel filter, poor fuel pressure. Stuff like that. But you didn’t even report the mileage on the van let alone any of that info so there isn’t really much of a place to start.

Is the check engine light on?

This is one of the most asked and answered kind of questions, but since nobody else is answering, I’ll repeat the answers:
First thing to do is check the ignition wires at night. If there are multiple leaks to ground, you will see the wires sparking where they are plugged into the spark plugs, and you should replace the wires.
If that’s not the problem, next you need to begin to determine what part of the emissions or fuel delivery systems are not doing the job. Is the CEL on? Is it flashing while the car is misfiring? In either case, get the car to a dealer and pay to have the car diagnosed. You can also go to AutoZone or Advanced and get the codes read for free, but the answer will be less specific.
Most commonly, your van experienced problems with the coil pack, crank and cam sensors, which are electrical, and the fuel injectors and even the fuel pump. I don’t get the impression you are going to be testing the coil yourself, but you can. If not, better get the problem diagnosed for you and decide if the repair is worth the van. A diagnosis will cost up to $100. Start there. Get as much information as you can.

ive got a 2000 impala that did the same exact thing a few years ago, i tried ignition parts filters dry gas but it ended up being the maf sensor would randomly act up on me. not saying thats the problem but the info may be helpful good luck!