2003 Ford Taurus SHUTTING DOWN

The Ford Taurus that I have is a 2003, SE, 24OHV. It shuts down, the car cuts off, then cuts back on, I can tell because the dash lights light up like Christmas tree. The headlights go dime, dash lights go dim, it sometimes takes a few minutes before the lights go back to normal. The car shuts down and then in just a few seconds it will start up. This happens when lights are on, radio, heat a/c, this is when I notice more. Sometimes I can go several weeks and it doesnt do it, then it can do it 3-4 times daily.