My lights on buzzer stopped working last week and then I was hoovering the inside of the car at the weekend and I jumped out of my skin when a car alarm went off. I looked around at the neighbours cars before I realised it was mine

I turned it off but it did it again and this time I heard the doors autolock before it went off. I had to put the key in the ignition while I cleaned the car.
Is the switch on the hinge end or the lock end of the door and is it easy to get to?