Anti-Theft Alarm Problem 99 Intrepid

I have a factory-installed anti-theft alarm built into my 99 Intrepid.
Lately, after arming the alarm with my key fob, the red light on top of the
dashboard remains on solidly for a period of time, and then begins to flash.
Normally, the red light flashes rapidly and then flashes more slowly. I
checked the manual and it says if the light on the dash illuminates solidly
when the alarm is activated, there is trouble with the trunk. A couple of
times, the alarm went off (lights and horn) when I closed the trunk lid
even though I disabled the alarm first. Does anyone here know a simple fix
for this problem or is a trip to the dealer on my 'things to do' list once
again?

Thanks in Advance,
Arthur