1998 Ford Escort Car stops

Engine Performance problem
1998 Ford Escort Automatic 164000 miles

One morning on my way to church, I stopped at a reputable gas station - SH%$^, filled the tank to half. I was driving and accelerating at about 35-40 mph, then my car jerked. I then exited off the freeway to a local Walmart, (I didn't know if my transmission fluid was low), a car tech checked the fluid and informed me that I did not need fluid, He informed me that I did need an oil changed. Later that night I drove home ok. 3 days later as I was driving my son to school I pulled out of my apartment complex and pulled to the side, the car was running and then completely stop. Nothing will come on. It was almost as if the battery died. I lifted my hood, blew some corrosion off ( not much there) and then I heard the chime in my car again. I started the car and drove. I had the alternator and battery tested with an oil change at Firestone and their report stated that the battery and alternator is good ( they are both 2 years old). I also had my transmission fluid/Filter changed. A couple days later as I was driving into my complex it did it again, the radio turned off, and I coasted to the side, I lifted the hood again and moved the battery cable a little and I heard the car chime again, then I drove into my carport.
Could you help me and let me know why my car dies while driving as if the battery died. I'm afraid to drive fearing I may get stuck somewhere.