When the security system triggers, it will start alarm sound + flashing lights which is normal. The system can trigger in many ways like opening a door, shocking the body, pressing the remote key button etc..
If it is automatically triggering, try to check following things in the order.
Check the shock sensor module. It may be too sensitivity. There is a small adjuster on it and try to decrease the sensitivity. Sometimes that module may faulty.
Check all door switches. They may poorly/randomly connect to body (ground) after the doors are closed too.
When last two times it alarm, were you sufficiently nearby to the car with the remote key ? The micro switches in the remote key too can stick randomly when its spring lost the tension. But this occur in lock/open switches mostly.