1993 Plymouth Acclaim sputtering and shuts off

1993 Plymouth Acclaim mileage: 232,000. I am not sure what is going on with my car. I'll be driving down the road for about forty five minutes and then out of the blue my car starts sputtering and shuts off. If I let it sit for about a minute it will allow me to go for about a mile. If I allow it to sit for a longer period of time it will run longer. The car is fine on short trips but it keeps doing this after thirty minutes of driving. My dealer told me it was the radiator and I let them replace it, but it didn't do any good and it ended up costing me $300 for a non-Chrysler radiator. Would it be an oxygen sensor? P.S. This car has been really good to me over the years and this is the first major problem with it in over 230,000 miles. Thanks