Yesterday I drove out in my 2019 Ford Ranger on to the street and coasted down the hill to a T-intersection. As I was coasting down the hill, I could hear the auto gearbox trying to make its mind up which gear to take. I came to a stop to give way to my right, and as I was moving away the gearbox gave a very big shudder which felt very uncomfortable. After that, the car was good! Mind you all this is happening in the early morning so the car is cold. I also had a Ranger 2017 and that car did the same. Ford could not find a fault code so it never got sorted. I will monitor this and see what happens but I find frustrating that the same has happened in this Ranger, too.
So, going by your description, the engine has only just started before the vehicle rolls downhill to the first intersection. So the engine has only been running for a few seconds, and then only at idle. It’s possible that the transmission pump hasn’t had time to build up enough pressure to fill the accumulators to eliminate any slack in the shifting clutches and bands. Which could, on the odd occasion, produce a clunk when you hit the throttle for the first time on a cold transmission.
Honestly, though, this is a problem you see more in older cars with worn transmissions, and I wouldn’t expect it from a 2019 Ranger.
But let me ask you a question: Is the vehicle lifted on its suspension? Many Ranger owners opt to raise their cars for greater off-road performance, but this changes the angle of the driveshaft and can cause precisely the shudder you’ve described. The fix is to fit a spacer between the car’s body and the centre-bearing of the driveshaft. That corrects the angle of the driveshaft and stops the shudders.