1. Check for any looseness with front tires, shake with both hands at 12 & 6 9and then 9 &3 o'clock with tires off the ground.
2. Check both Flex joints for play and cracking. Major safety concern as bad flex joints can result in catastrophic failure with major damage to car.
3. Lower and/or Upper Ball joints may be worn, as could be the lower control arm bushing.
4. If suspension and flex joint are tight then tire balance or other tire defect may be the culprit. But I would check the other items carefully first.
5. Transmission problems are also a possibility.

Hope this helps

__________________
Martineau Gauda
mgauda@sprintmail.com

96 C280 Mercedes
82 Rolls Royce Silver Spur