Security light?

I have a 1997 Caravan with 120000 miles. When I start it, it sometimes runs for 3-5 seconds then shuts down. I noticed that the "Alarm Set" indicator in the dash will sometimes start flashing when driving and just before the starting problem shows up. Could it be a problem with the factory alarm system shutting down the engine? I also need to know where to look for the Valet switch for the alarm so I can switch it and see if that makes a difference.