Hello clublexus, I'm a proud owner of a 2009 es350 (2grfe) with 76009km, but recently, I took notice of its intense vibration in the steering wheel that is also resonating throughout the cabin, it only happens while idling in Drive mode or reverse mode and in optimal operating temp (it doesn't happen tho while the temperature is still climbing or is cold) but its smooth in neutral or park or even while I'm cruising along and getting into speed. I am kinda lost right now, since my mechanic checked all the mounts and suspension parts and they seem fine, I also changed my tranny fluid and filter. Hopefully anyone could help me out and thankss in advance and I really like this car.

 

Check your exhaust, I had this recently and it ended up being my flex pipe developing a hole (and had to be replaced), but I had some of the same symptoms, with a new exhaust it runs a bit smoother. There's also a harmonic resonator on the tail pipe which is designed to reduce vibrations from exhaust, it's a piece of rubber attached to a counterweight which may be on its way out.

The car does vibrate when it's in gear, it's a V6 not a V8 after all so there's some imbalance to be expected when the engine runs, as long as your mounts are OK and there are no engine misfires then you may have to wait for it to develop a bit more before you can determine the root cause.

 

It is likely your mount(s).