sounds like the battery actually.
on vipers/dei alarms, when u pull the battery and reconnect it, the alarm automatically goes off. when the battery is low, and you start car, the voltage drops. when the engine stops cranking, the voltage goes back up. the alarm thinks the battery was unhooked and hooked back up. try jumpstarting your car. it might work.
also, an easy way to tell if your battery is drained is by the brightness of your headlights