Passenger airbag is only sometimes ON

I have a 2007 that I purchased a few months ago as my first car, sometimes when driving with a passenger the airbag will read ON, sometimes with the same passenger it will not read ON.

When it's not on, we've tried moving the seat forward/back, bouncing up and down, turning the car off and on again, none will turn it on.
Then the next day driving it'll randomly start working again.

I hope that maybe a connector to the seat sensor Is loose, but there are 4 or 5 connectors under the seat, and looking at the wiring diagram sheet I had no clue how to find information about which is which.

Does somebody have a diagram of the layout of the connectors under the seat? Does anyone know any ways to possibly fix this? Is this likely something any mechanic could fix, or should I go to someone specialized in electronics, or go to a dealership?

thank you!