You definitely want to get the tires looked at.  Not just for balance but
for uneven wear that could point to alignment (or worn parts) or radial
force variation issues.  I am not sure of your location, but when there is a
decent amount of snow, it can become packed in the rim and throw off your
balance, also.  I have had to go to the car wash just to get rid of the
vibration numerous times this year.  Good luck.

Unless your '04 is vastly different than my '02, you have little bumps on
your roters and need new ones.

The bumps are caused by excessive heating (or so it was explained by my
mech.) due to the weight of the car when braking downhill.

I had then replaced about 30K miles ago and have followed a bit more of
this regiment. When braking downhill - particularly from freeway where I'm
gong from 80 to 0 - I'll brake, then drop it in fourth (take the OD off),
third, then finally low when I get around 30 MPH. Essentially that is like
a manual, and I'm letting the engine help the brakes.

This has helped  out a lot in keeping my roters from overheating, as I
live in a very hilly area.

Sounds like your rotors are slightly warped. They're not too expensive
so have them replaced. When you say "new brakes," I'm guessing you
mean pads; which, alone, will not fix the problem.

Keep us posted!

-- Christian
'02 Sedona EX

Look at your tires for uneven wear (one side of the tire has less tread
than the other.)  If the tires look ok I would take them to a tire shop
and have them balanced.  If the problem persists the cause must be with
your breaks, probably warped rotors.  You may need to have them turned
(if possible) or replaced.