Cougar just dies but will restart after setting

[eeezeegoin76]

My step son has a 99 cougar with a v-6 automatic;sometimes right after he starts it up and it runs for a few minutes, it will just die.When the key is turned to try to restart it the dash lights will come on but that is it, the moter will not turn over, but you can hear the fuel pump running but it will not start. You can let the car set for a short period of time and it will start right up. The car was taken back where he bought it they played with for about a half of a day and told him that nothing was wrong with it. I got playing around with it one day and took a rubber mallet and tapped the computer under the dash,the fuel pump will stop and the car will start right up Could this be a computer problem or something different thanks