Please help..what could this car problem, be...I am so upset as I am wasting all my money and not fixed yet?

From what you say here, it does not appear to be a battery problem. If the headlights, etc work ok when you have a problem, its not the battery. If you attempt to start the car, and it makes 'no sound' at all, and tapping the starter motor makes no difference, it is not the starter motor. I'm not a mechanic, but if it was my car, I'd be troubleshooting the electrical system from the ignition switch forwards. Automatic cars have a neutral safety switch. This switch will not allow the car to be started if it is not in park or neutral. When activated, nothing will happen when you turn the ignition. I had a misadjusted switch on my old car, and it would not start in neutral. I'd be taking the car to a competent auto electrician, and asking them to take a look at the electrical system. The so called mechanics you have used so far have been rippping you off. As a side note, the problem could be due to loose or faulty wiring, near the vicinity of the radio. Next time it stops, lightly hit the dash area around the radio, and see if it makes any difference.