Curious thing happens after work in the parking garage. If I start my car and immediately back up the brakes have little to no brake power! Or, at least it doesn’t seem like it - the pedal doesn’t depress right/etc. After the first time, the brakes work again. If I start the car and pump the brakes, then no problem. I don’t have a problem with my brakes in the morning at home either, just after work in the parking garage.

Its a 2009 with 130k miles on it, so its driven well.

Any idea?