My alarm on my 2002 Hyundai Sonata keeps going off

Experience with this problem points to several possible causes. First, hood switch is improperly adjusted or rubber button on the underside of the hood which strikes this switch is missing or worn out (does the 'answer back' feature (horn toot) occur when you press the "lock" button on the keyless remote twice?). If it doesn't, this is the first place to look -- is the hood bent out of shape? Often I have found the hood adjustment is SO CLOSE to the hood switch being 'CLOSED', that a simple gust of WIND can set off the alarm.
Next, each door and the trunk have switches which must be in their proper positions (closed -- Open Circuit communication with the ETACS module) for the burglar alarm to SET Active/ON. The problem could be at any one of these switches, not to mention the ETACS module itself. Best solution:Take/tow the vehicle into a Hyundai Service Center (dealership), pay the diagnostic fee. They will tell you EXACTLY what the problem is and what's needed to fix it (parts, labor, tax, time-frame, etc.).