factory security 98 chev 1 ton dually

Sometimes the factory security system light flashes when you first turn on the ignition switch,this will not let the vehicle start,if you turn off and let it sit for about 10 min this will reset the system and the vehicle will start.It happen often.The dealership wants about 300 to 400 dollars for a fix,not telling what they can do.Anybody out there that can relate.Help