so over the last few weeks i've noticed that when my car is accelerating and braking, during a particular speed range, and also often at high speeds, the car seems to be sort of shaking. during the braking it is most noticeable. because it happens not just while braking, i'm guessing it's not the brakes. my car only has 37k miles on it. if i had to guess, i'd say the tires need to be balanced. would an alignment be reasonable, also? obviously i can bring it in, but i'm not looking to spend money needlessly, so i'd like to have some educated opinions from folks on here.

thanks for any help!

Start with the balancing...

Sounds like you may have two problems one would be wheel balancing and also I think you are going to find you have warped brake rotors, I say this
because brake problems are very common on the 07ES I would not be surprised if the 08's are the same.