If the front struts have never been replaced, a worn out strut can cause this type of vibration. If the struts can no longer dampen the front spring ocillations, the tires can reach a certain rotational frequency where the tires can start to bounce up and down rapidly at that frequency as the vehicle is being driven. This is called tire hop. If you speed up or slow down, you go out of the frequency of rotation that causes the tires to bounce and the vibration goes away.
Here’s an example of tire hop.
Tester