check the lug nuts for tightness
Very good advice.
Also, in the many years of driving I have run into three other issues. They are rare but did happen to me....
1) On a Chrysler 300M 1999, we had a front disc caliper freeze in the closed position. At 55MPH we encountered a horrendous front end wobble.
Not at lower or higher speeds. This was caused by the break pads being frozen in the closed position.
2) On a Toyota Supra Twin Turbo, a front disc threw a balancing weight. At 45 and at 85+ MPH the front end would have a very mild wobble.
The vented disc has heavy wire weights added to the vent fin(s) at the factory to balance the disc.
One of these apparently worked its way free causing the disk to become unbalanced. In this particular case, the entire rotating assembly
became unbalanced and the fix was to replace the disc and hub bearings.
3) On my Jensen Interceptor 1973, a front radial tire had a radial belt delaminate which caused the front tire to have a wobble at 20 MPH and above.
Horrendous ride quality. Easily found and fixed. Was covered under warranty.
Again, the above three causes are very rare but they did indeed happen to my cars.
Just goes to show you that a lot of things can cause this.... Checking the lugs is really easy to do. And the least costly as well.