I've found that my wife will trigger the same "airbag off" light when she gets in after the car has been running for a while. If she gets in before I turn the car on, it operates as usual. Glad you mentioned this since I need to have Nissan address mine as well.
She's around 115 lbs
Disclaimer: Honey, if you read this.... I'm listing your weight for technical reasons and should by no means be read as me having issues with how much you weigh!!
While the couch is comfy, I'd love to sleep in my bed tonight!