Could be a wheel weight missing, a bad ball joint or a bad shock.
i would really like to know myself
Wheel balance
Out of alignment.......warped brake rotor......broken belt in a tire.....
have your front tires rebalanced.
Warped rotors
allignment
Three things to check, Wheel balance, Alignment, or most likely the front rotors may be slightly warped.
Tire out of balance or bent wheel.
Most common reason is improperly balanced wheels, next would be alignment but that usually causes a pull to the left or right.
the tires could be out of balence bent rim bad tire
Could be a small thing like wheels out of balance 40+ "Noisy Inside Car" bad wheel bearings 30+ mph also decelerating harder to control "Steering wheel wobble "on accelerating / decelerating" "Noisy Inside Car" steering linkage: causes the steering wheel to wobble at 40+ mph decelerating harder to control "Steering wheel wobble "on accelerating / decelerating" My brothers car had the above problems I changed his rear spindle, outer, tie rods, "both were shot" bad bearing "blown bearing"
Wheel bearing.