Welcome to the Forum! Glad to see you made your first post. Sorry to hear you have an issue. Definitely take the TLX in since it is under warranty.I'm experiencing the same issue - not only at idle, but while cruising on the highway between 60-70 mph. I recently upgraded to my V6 TLX from a 4-cylinder TSX, so I'm not sure it's to be expected.
Similar to Mika C, at speeds above 60-65 mph, I'm having considerable vibration in the driver seat, steering column, gas pedal and visibly apparent with a significant shuddering of the front passenger seat. Severity of the vibration is related to road surface but it has the vibration on very good, smooth, new Houston highways. I just bought it and didn't feel it on my test drive because I didn't drive above 60 mph.
Welcome to the Forum to both of you! Glad to see your first posts.I am having the same vibration issues with mine! I have only had it 5 weeks! Exactly like you described! I have the 4 cyl base model. They said it was a tire balance issue but that didn't fix it. Took it in again and they didn't do anything to it because they said the tech didn't feel anything when he drove it.