One problem related to side/window air bag has been reported for the 2004 Cadillac STS. The most recently reported issues are listed below.
On 12/5/04 I parked our new (561 miles) 2004 Cadillac deville at the covered west palm beach airport parking lot. I left on business and returned to the car at 7:30 pm on Thursday, 12/9/04. I got into the driver's side, put the key in the ignition and started the car. The two front and passenger side airbags airbags deployed! the driver bag raked up the inside of my right forearm (which was still holding the key in the ignition) and then hit me in the left side of my face. I was suffering from a terrible cold at the time and had to sit there and inhale the dust from the bags until I could get them all deflated. I managed to drive the car home and drove it to the dealership the next afternoon, where it remains awaiting parts. Gm has called me twice, the first time was a young man who didn't know what the heck he was doing other than reading questions off his computer, and the second time the engineering department called to ask more stupid questions. . . Like, "what kind of car was parked next to you?" and "was it humid?" I explained that in florida, it's always somewhat humid. The abrasion on the inside of my arm bruised and also ended up peeling on 12/22/04. My left cheek bruised and then the spot got little tiny, unsightly pimples that went away around 12/19/04. I am still coughing. The dealership authorized us to get a rental car for the duration. (your form will not allow me to enter "deville" as the model of the Cadillac!).