Twingo Ez 05/05 Airbag lamp

Moin, our Twingo EZ 12/05 starts spinning in the warm seasons. It is about the airbag control light as soon as the warm months start so from April to Oct. or Nov. the lamp sporadically goes on and off again as if a wobble contact would exist. In the cold months this problem does not occur, TÜV is always in December and therefore we never had the problem at the TÜV xD !!! But of course it is not nice to drive around without working airbags therefore my Question where can the problem be found. I’ve read that it can be a grinding ring in the steering wheel then I think that the problem would persist permanently. A colleague of mine meant that it could be a wobble contact on a plug under the seat only where can I find this plug or wackler?? Other topic ..We want to sell the Twingo in two months he has now 120t Km down and has had a few accidents which however have never prevented to come over the TÜV. re such a realistic price ? Can I still get 700 euros for it 1.5 years TÜV he has still matured and 8 compartments