Whenever I drive in hot weather or for an extended period of time in any weather, the steering wheel will begin to vibrate or shimmy somewhat. I can really feel the shimmy when I make turns. When I make a turn it feels like the tires are almost flat or have flat spots on them. This problem goes away after the car cools down. Has anyone experienced anything like this? Whatever it is, it can't be good.

 

have you checked your front bearings? might be that.

 

How are your tires? A slipped belt in a tire can do this, and get worse as the tire heats up.

You might try rotating them front to back and see if there is a change. Check your wheel bearings while the wheels are off....

 

Sounds like a seperated belt. The boundry layer between 2 belts have lost adhesion to each other. When the tire heats up, this causes a bubble between the 2 belts.

Next time this happens, pull off and check the tires for bumps/bulges. They don't have to be very big to to cause ride degredation.

If the tires are under warranty, take them back to the dealer, there may be a recall on that batch of tires. If nothing else, they should prorate the tire based on treadwear.