[Papa Rad17]

Your tires could be out of balance, warped rotors, maybe the hub bearing going out. You however should driving the car now before you cause expensive damage. I speak from experience. I noted something like what you are describing on my way to homecoming 2014. I had other problems on the trip (Previous owners neglect and wreck) that led to getting new tires. While my car was on the lift they called out. They proceed to grab my tire and shake it front to back, tire rod end shot. Then reach over and grab my entire rack and pinion assembly. It had about a half inch of play. Being a couple hundred miles away from home I couldn't deal with it, and limped home. A week later I got under the car to find the rack and pinon had an inch of play in the drivers side mount. The bolt was trashed, the rack its self had been ground out 2X larger, and had to build a completely new mount to weld onto the sub frame after grinding away the trashed metal. I know this is an extreme circumstance, and overall it was $400 fix because of the extensive damage + new tires. pictures may be around here somewhere still.
What you should take away from this is to stop stop driving the car until to know what you are dealing with. Get both front wheels off the ground, and make sure thing move that should, and the don't move, aren't moving.