I had a jeep that had the death wobble, it was very scary, I started with the simple, tires, wheels, etc, then the steering damper, but it turned out to be needing front end work like ball joints, etc. Now it is fine!
Town fair tire offers free or reduced Alignment , with purchase of tire, and although I am not a fan of theirs, they can tell you what the car needs, and they don't repair so they will not try to sell you what you don't need. Go to Walmart and have them balance tires, if they are newer. Or like I said Town Fair get tires, get them balanced and a front end alignment. HERE IS A LINK TO EXPLAIN POSSIBLE CAUSES.
I ASSUME YOUR CAR IS OLDER AND HAS NOT BEEN IN ANY ACIDENTS, GOOD LUCK, Steve