What could be the reason for the idling vibration in a Nissan Sunny manual transmission? I've replaced the spark plugs, but it hasn't solved the issue.

When decelerating at speeds of 20-30 km/h in a 2011 Nissan Sunny with a CVT transmission, there's a noticeable jerking sensation. It doesn't glide smoothly when you let off the throttle.

What should I do if the sunroof of my 2011 Nissan Sunny is rusted? I bought a second-hand car. Does it need repair?