wiring/door issue- interior light on and off
 

For a while now, when I come to hard stops or ride on bumpy roads,my interior lights come on and goes off. It used to be intermittent. Now it happens more often. . It actually seems that when i get up or down from the seat of the car it turns on/off. I've fiddled with the door sensors which seem OK. Could there be wiring running under the seat (stock wiring) that has a short or something? It's very puzzling since I've never done any electrical modifications to the car. Any suggestions?