Reviving an old thread, I am having the same issue on my 400h. Violent shaking at startup when the hybrid motor kicks in whether cold or hot. Took it to an indie shop and was told it's the "hybrid motor" which costs $2k-4k. Also the engine mount is bad, too.
Sounds like I need a second opinion!

 

Start with engine mounts (all, OEM)

 

I've decided not to spend any more money on this Lexus money pit and get a new car next year. In my own personal experience (definitely in the minority), Toyota/Lexus reliability is greatly overrated.

 

Good luck!

 

Just picked up a low-mileage 2015 RX350. Fully loaded, drives like new.
Don't get a hybrid if you plan to keep the car for a long time, fewer parts to break/worry about.

 

Those are known to have a lot of oil leaks, timing chain cover etc.....

 

Yes it had been repaired under warranty.

 

Nice car, enjoy.