is this the first it happens? ever happens when you ride other bike/scooter? any previous injury on the right shoulder?

imo, correct riding position is when you dont feel any tightness in your arm and legs during normal riding and cornering.

maybe your seating position is too far back that your right arm is more stretched out than usual riding position.
consider adjusting the handlebar positioning, turn the handlebar so it move closer to you or use handlebar riser if needed.

or could just be muscle weakness and this pain will be gone once your body is used to it.