This is a problem you are likely to experience with the realtively simple (primitive?) set-up on the A-4. Things might be different if you had a two barrel or 'progressive' carb, or one with an accelerator pump built into the carb.

Lets look at what happens when you open the throttle. Now some carbs (like the 1-bbl Zenith on my '72 Land Rover) have a small piston pump worked by a cam off the throttle cross-shaft. Open the throttle and a small amount of extra fuel gets directed into the carb throat to go with all that air now moving throug.

The A-4's Zenith carb doesn't have this, and as an updraft carb, it merely pulls more fuel from the bowl by vacuum. So there is a delay until more fuel can be drawn into the air charge. For a short while, you'll be overly lean.

Of course, as you increase the speed the pistons are moving, you have to advance the timing of the spark that ingites the fuel/air charge. This is where the centrifugal weights in the dizzy need to be in good condition. If the weights are sticking, this hesitation is liable to be bigger/longer....

Short answer: just advance the throttle slowly.

Cheers