1998 Dodge Stratus it dies

My car will run fine for days or weeks, it varies. Other times after driving it for 5-7 minutes the rpms will go down. Sometimes they will come back up and other times the engine completely dies. Sometimes we have trouble getting it to start back up. We have had certain things done to fix the problem but the same problem always resurfaces after driving it a few days. We have had the fuel pump and filter replaced. Also the distributor cap. The fuse box under the hood has had the connections cleaned and all spark plugs have been replaced. We have heard that this year, make and model has had similar problems but no one has told us what to do to actually fix this problem.