If you have a thump sound and it happens often enough to hear it - yes, take it to the dealer for diagnosis.
NO way for us to determine what is causing it - if you are driving the car and it stops and starts normal then it's a small problem. Just get it looked at as soon as you can,
NO way for us to determine what is causing it - if you are driving the car and it stops and starts normal then it's a small problem. Just get it looked at as soon as you can,