Had '05 g35x for about two months now. Loving it.
I do alot of highway driving, and lets say I'm going about 120-130km for a while and run into some traffic... while idling on the hwy (or very slow speeds), the car begins feeling bouncy.

Is that normal?
If not, what could it be?
No noises.

Thanks guys!

 

Road surface?

 

No, don't think that's it. Was driving a different car last year on the same highway with no similar issue.

 

Does the car do it on other roads at a similar speed?

 

Could be a miss, might be time for new plugs. How many miles on your car?

 

95,000km on it. Havn't checked the spark plugs since I bought it two months ago.

So basically the problem happens while i'm idling in traffic with my foot on the brake, or while letting it roll.

 

If the plugs have never been changed, it is time to do it. The plugs are meant to last 100k miles and you are right around that point. Make sure you change one plug at a time and reinstall the coil pack as you go. Doing several at one time can lead to mixing up the coil pack firing order. Start there and let us know if i resolves the problem. Get NGK platinum or iridium only. Standard NGK are fine if you don't mind changing plugs every 20k miles.