1996 Chevy Lumina alarm?

Every time I open one of the doors the flashers will begin to flash, the interior lights will flash and all the gauge lights will flash for about 1 minute and then will stop. I can start the car and drive it while lights are flashing, but as soon as I open one of the doors it will begin to flash again for about a minute. Tried locking and unlocking doors with key but can seem to reset it. The car doesn't have any service engine lights on or alarm lights on. Any suggestions?