A) Taking it to an automotive repair shop for an estimate? I bet it's free!
B) Asking under the correct section? Cycling = BICYCLES.
But...as a former Good-Year store mgr. (many moons ago) it could be caused by several things.
1) Tires out of balance
2) Tires worn out
3) A faulty suspension part - i.e. a loose (worn out) tie rod end, bad ball joints, etc.
4) Or as suggested - time for new shocks and/or struts. Afterwards you'll need an alignment.
At all the stores I used to work at, we performed a diagnostic check on these items for either a nominal fee or sometimes even FREE. The internet will NOT fix your car. Go To A Repair Shop. Wow...amazing.
If the back end is riding low. Then it would be the air shocks in the back. If they don't fill up then the car
will ride very bumpy. It is very inexpensive to swap them out for springs. I have done several.
Maybe you should ask this question in the automotive section
Time for new shocks or struts.
