my 03 tl type s shakes when i first start driving in the morning when it's below zero out. Feels like the wheels are out of balance, but then the problem goes away after 20 miles.

I have never used any fix a flat or anything like that in the tires.

The problem is only noticible when i hit 50mph or so

 

Are you talking about the shaking from the wheels or from the engine, or the rpm?

 

I'm pretty sure he's referring to his tires.

 

mines does that when its really cold but soon as the tires warm up it stop ...thinking its just form tires been cold

 

Tires take a "set" from cold. Evens out as they warm up and become more supple.

 

I wonder if your tires have flat spot from parking just overnight.

 

thanks for the post