Car stalling after new alternator and battery installed?

This issue has happened three times in the past two months. I was driving on the interstate, and I was trying to accelerate but the car was just slowing down. The battery was functional for a few minutes (hazard lights were usable), and then everything shut off and I was not able to push down the brake to use the push button to start my car. I had it towed to a shop where they replaced the alternator and said the battery was fine, just needed to be charged. I left the shop and was on the interstate again when the exact same issue happened. I had the car towed home and purchased a new battery. After putting the new battery in, I had no issues with my car for around three weeks except for every once in a while my dash lights (brake and battery) would flicker but never fully come on. Yesterday I was on my way to work, and I was trying to accelerate from a stop and my car would not go faster than 2 MPH. I pulled over and turned my car off completely, the battery still worked at this point. I was able to let the car rest for around five minutes and then I started it up again and was able to drive around five more miles until it once again stalled while driving.