Car tends to randomly shut of while driving or idling?

i have a 1998 dodge intrepid 3.2 L, for about 4 months my car has been randomly shutting off while driving or idling as well as the rpms and speedometer have been acting funny. ive taken it to the dealer and they told me that they could do nothing about it. i recently had the alternator replaced from talking to a mechanic. turns out that wasnt the problem. so, when that didnt work i decided to do some research on the symptoms my car was having. of course there are multiple things that could make this happen. so i started off buy replacing the cam shaft sensor since hundreds of blogs were saying that it is common for this year make and models cam shaft sensor to go out and cause these problems. Next i replaced the battery the battery was p lts life expectancy (5 years old), that actually helped the problem i noticed that the car performed better as far as the sluggishness. but the car still shuts off randomly just not as much. the speedometer and rpm gage are still acting funny. Can anyone please give me some advice on what could possibly be the cause for the random shutting off???