When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
If you are still on the stock tires you may be getting flat spots when the car is parked for a long period of time. Does it go away after you have driven for a while? Mine does it too and I still have the stock Bridgestones on my car.
If it is the engine shaking only on cold starts or on heavy acceleration it could be an overly lean fuel mixture from any one of a number of sources....from gummed-up injectors to defective engine sensors.