Got all packed up and started up the engine to head home this morning and was greeted by the airbag (SRS) warning light. I figured a ground squirrel had maybe messed something up as they were quite fond of the engine compartment. Turns out the swivel seats can easily cause the airbag control wire underneath to become disconnected, or so I learned on the sprinter forums.
Sure enough, I looked under the driver's seat and found the yellow connector was disconnected. Plugged it back in and it appears the airbag (SRS) warning light is gone. It lights up when I turn the key (not sure if it always did that) but promptly goes out when I turn it over or wait a moment.