For the last three days, the brake light inside the car came on. The parking brake was fully disengaged. It happened when the car had been sitting overnight. Sat and Sun it came on once I started driving. It went on and off a few times and went out for good within a mile. This morning, it came on at startup and stayed on for about 3/4 mile. Once it goes out, it doesn't come on the entire rest of the day even if it sits for a while. The brake fluid is at the upper limit and the brakes feel fine. And ideas?