I don't feel any vibration when braking. The squeaking doesn't seem related to the brakes. It is intermittent and I haven't figured out the pattern yet other than it only occurs when turning left.

I took the car to the dealer. The mechanic checked the suspension and brakes and said it all looked good. I drove around the lot with him and, of course, the car behaved perfectly. He did find a valve cover leak that was dripping oil. He ordered a part and I'll be taking the car back next week for that. I almost hope the squeaking becomes more regular and louder just so he can hear it!