1999 Chrysler Concorde I don't know where this problem is

1999 Chrysler Concorde 6 cyl Automatic 154000 miles

I just purchased a 1999 Concorde. I thought I got a good deal on the car, but not even a week later it is cutting itself off all of the time. The car is not just stalling when I stop it, but it is cutting off in mid-motion with my foot on the gas. I took it to a mechanic they said they reading they got was that it needed a Cam sensor, but the sensor on the car is brand new. Then they said maybe the PNC computer is going bad on the car. I did not let them do any repairs because it did not sound like they were sure that would fix the problem. What do you suggest that I do? And what do you think the problem could be?