You need to plug the car into MES, it could be one of many things causing the airbag light. Apart from the 7 airbags it could be the seatbelts, pre tensioners or the ECU, plugging it in will tell you what the problem is. If an error is reset without fixing it, then the light will come back. As it didn’t immediately come back it’s obviously intermittent.

The ECU is held in by 3 x 10mm bolts, 2 are easy the one at the front is tricky to get to. Disconnect the earth of the battery before messing with it. Once the bolts are undone go to the right hand side and undo the two electrical connections. Be careful as it’s easy to bend the pins.