I had the exact same problem. But it would be on and off. I thought my gears were stuck or I had a transmission problem. I took it to the Dealership the same day. I had an extended warranty. They fixed it while I waited. It was at no cost to me, and they said the issue was a faulty brake light sensor. The part cost $60. I remember they gave me an invoice and zeroed it out. I should still have the invoice in the car. Need to check it out later on.
Haven't had the problem since. You said you only had 30K miles on it. That's covered under warranty then.