I have a 2021 IS 350 F Sport that makes a clicking noise on the interior when the car is cold. The noise appears to be coming from the firewall or the floor on the passenger side. Once the car warms up and is stopped/restarted, the noise usually goes away. Any ideas?

 

Could be the catalytic converter expanding as it warms up. Also makes the same noise when the engine is turned off and is cooling.

 

The V6 engine makes this sound by design, if it is a slight sound you are talking about - it is more noticeable when the engine is cold.