Will stutter almost like it's misfiring spark or not getting any fuel?

The car will stutter almost like it's missing spark or not getting any fuel. (Engine light turns off and on)It does this about 2-3 times a week.I was told it was an ignition coil that needed to be replaced so I replaced it. A day later the car stuttered again.(Engine light back on) I took it back to the shop I was told by mechanic that the coil was fine that it could be a computer problem. A few days later my car made a loud clacking noise when I put it in reverse when I gave it gas the car didnt go and the engine didnt rev. I turned the car off and back on and it ran like normal. I then took the car to the dealership who assured me it was not a computer problem.I was told to replace the ignition coil and throttle body. Being that I had already replaced the coil I didnt feel too comfortable with their diagnosis and left without having the car repaired. I took the car back to my mechanic and had the throttle body replaced. A week later my car stuttered and again wouldnt move when I gave it gas (engine light back on)turned it off and on and car ran fine. Car is back in the shop and Im being told ignition coil # 3 is bad. HELP