This only happens when my car has been sitting around for a little while

but when i put the car in 1st gear and accelerate i can feel a slight rub at a certain rpm like 2000 or right below it.

I feel it through the gas pedal and it feels like something is rubbing then it gets past the rubbing point and it drives fine afterwards. Wont happen at all until i leave the car sitting around again for a couple of hours.

Once again it feels like a slight rubbing of 2 parts or something while accelerating, very hard to replicate to dealer so i've had to live with it.

Any ideas?