So basically the engine is causing the car to shiver when stopped. Its not completely reproducible and happens sometimes, others not so much but the only way I can describe it is shivering which can be felt lightly in the seats.

Any ideas?

 

What year is it and how many miles do you have? It could just be a tank of bad gas!
First try a bottle of fuel system cleaner that you pour in the tank. Give it a week to work and replace your gas with fresh stuff as soon as possible. If no improvement after giving it a week to work, it is time for professional diagnosis.

 

It doesn't like your cold and rainy weather!

 

2012 RX450h F-Sport with 32k miles on it atm. Ive been using regular UK unleaded which is equivalent to US premium unleaded. Ill stick super unleaded 98 RON and see if the additives help over the course of a few months.

It only happens on idle, no issues when driving and power is definitely there.

No lights on the dash either.

 

FYI, RON95 (UK Regular Unleaded) is the equivalent of US AKI 90-91. AKI 91 is the minimum rating for Premium in US and the RX450h. Super Unleaded would be a better fit.