If this is happening or happens check your brake fluid, It's a sign that it's low or lower. This will happen even if your fluid is not at the minimum level, and the fluid is still cold... sometimes the lights will stay on when you start the car and sometimes they will just appear... and every once in awhile after your fluid gets warmer just the brake light will go away leaving the ABS and slip one still on... And If that doesn't fix the problem check your brake pads and brake sensors...