My car has steering vibration ONLY when the tires are cold first thing in morning. This goes away after driving few miles. Does anyone know what the cause could be?

 

Likely a tire issue. Rotate tires front to back to help deduce problem.

 

Flat spots where the tires were pressed against the floor or driveway while parked overnight. As the tires warm up, they return to round.

 

Having a similar issue with some new 21" tires. Bought from Tire Rack but were not Porsche designated (N0, N1, etc.). TR said that was okay. However they vibrate above 65 mph. Vibration is bad if tires are cold or haven't been driven for a few days, but eases somewhat when tires warm up. Dealer has balanced them 4 times and rotated them with no benefit. They also returned one tire to TR as unable to road force. Dealer will try for a fifth time next week after receiving new weights for their balancing machine.

 

I noticed this same problem after my car sits for a few days. These are the stock 21" tires that came on the truck... I don't think you can balance it away.