Recently bought a 1998 V90. Love the car, just curious about one odd detail in the driving experience: I occasionally hear a sharp, single click/snap from the upper interior area adjacent to the headliner, near the driver's head (mine!). Timing seems totally random, maybe roughly 5-10 minutes apart, happens whether moving or not (but only when engine is running). Is it part of the side-curtain airbag, maybe a sensor resetting? Thanks for any insights you can offer.