Car shakes when idle
Recently, I noticed that when i am stopped at a red light, my car vibrates/shakes more than usual(a bit too much in my opinion, it is almost uncomfortable to sit in the car when it vibrates). It feels like the car is about to stale. The vibration/shaking can reduced when shifting to neutral. The vibration/shaking is not constant, it would starts to vibrate for a second or two, then stop, then start again. And the cycle goes on.
Does anyone know what could be the cause?