Intermittent running issue on the Dart

the 66 dart has been sitting for a few months. The slant starts up relative easy. Got some new gas. I decided to take it out once a week. Last week driving and the engine felt like it was bogging down and would not let me accelerate past about 35mph. I pulled over, shut it down, restarted and drove off it was fine. This now happened again this week. Same thing, bogging , won't let me fully accel, even if I mash the gas pedal all the way.

Any ideas on why this would happen sometimes and not others? And why restarting the car fixes it??

it is swapped to electronic ignition and has the Super 6 carb.