I have stereo system installed in my car and it was working just fine but then one day it started getting electrical interference and now my subs go off by themselves really loud even if the volume is down all the way it still goes off with a constant base it loud too what's the problem? I have to 12" subs with to 1200 watt amps connected to each one

Diconnect the inputs to the amp and see if it still does it if so the input is telling the amp to blare loud. More likely the amp is going bad and is starting to go full throttle on its own. This will kill your speakers be very careful.. are both amps wired bridged?