Welcome. I suspect either tire issues or wearing steering gear. I rarely hear of steering parts wearing at your mileage, though.

Swap the tires front to back and see if that changes anything.

 

 

What tires are they? Some tires are more prone to tramlining, and this may be something you're experiencing if it's gotten worse since your new tire purchase. Do you have your latest alignment sheet, low caster can cause a wandering feel, good to know what specs you're currently at.

Welcome to the site btw.

 

 

 

Looks like a good alignment, caster is low but just in spec. Not sure if there's a way to get more caster w/ OEM parts (I have high caster adjusted w/ aftermarket arms), if there is a way to get the caster closer to 5 w/ your OEM setup I'd consider that.

 

Any chance there’s an issue with one of the rims? I would assume they’d catch it but you never know. Have you asked them to road force balance the tires?

 

 

following for info. got the same issue on my 09 g37x coupe. My wheels also shudders at high speeds tho. I have been worried I have a bent rim but not sure really. I have really durable tires tho (continental extreme contacts brand new) so not sure the issue. I recently had my alignment done and it helped a little but car still sways weirdly. Mine is lowered on bc coils tho without a camber kit or aftermarket arms so my issue may be related to that

 

It might be a small enough bend that it's not visibly noticeable but still effects the car. I had a similar issue and went to a couple dealers and they found nothing. They kept saying it was because of the "crown of the road" but I was able to duplicate it on a flat surface or on a highway where in the left lane if anything it should veer left but mine would veer right. They rotated the wheels to see if it would now veer left but it didn't make a difference. One dealer suggested grabbing a wheel (or all 4) from another G and see if the problem went away but they didn't have one at the time.

I decided to wait until I got new tires. The problem never fully went away with two different sets (summers and winters) but did get drastically better after a road force balance and alignment (I vaguely remember the service advisor mention new alignment specs) to the point where I hardly notice it unless I'm focusing on it plus I'm not on 100% stock suspension anymore so the dealer probably wouldn't help me anyway.