I think that if there was am actual fault in the airbag system then the light would come on and stay on and the DIY reset wouldn't work.
The connectors under the seats take a lot of punishment from passengers, moving seats and stuff getting kicked under especially if it's a busy family car.
Check to make sure that all connectors under both seats are still attached to the frame and that both parts are securely in place.
DON'T unplug them unless you've disconnected the battery first!