vehicle is squirrelly

Are the tires all the same size/type /make? Do any tires show signs of unusual wear? Quickest thing you can do your self is rotate the tires and see if anything changes, after that I would strongly recommend a 4 wheel steering alignment to see if any thing is bent or out of specification, tell the alignment shop what is happening and get them to inspect the steering components for wear. I replaced a lot of suspension components on my brother's Audi with relatively low mileage.