1988 Buick Century car dies when u put it into gear

This has happened a couple of times now its not a very fun thing to experience.
when we had got the car they said you have to push theshifter up hard and hold it in order for it to start(they said it was the nuetral safty switch). So after driving a good amount of time it will jus die on the street not sure why but then you get it started again just fine and as soon as u shift it out of park it would die. After we leave the carwhere it brokedown overnight or so come back and start up and drive away. Its very confusing.
if u have any suggestions that would be helpful I would really appriciate it