I think I've experienced this before. Bigla na lang bumusina yung car (without anyone doing anything to it) hanggang sa napilitan kaming tanggalin yung isang terminal ng battery. Turns out it was the 'way' of the alarm telling us that the car battery was about to get flat. Weird talaga. Because when I bought a new car battery na, I bought the car at Autopage distro at del monte ave. And they cycled the alarm module and it was normal naman.