Volvo XC90 dash, windows stop working

Recently I had the dash lights, A/C blower, electric windows all shut down while driving. The car still drove ok, but nothing worked on the instrument panel, electric windows. After parking it overnight at home, all seemed fine except for a message saying the airbag needs servicing.
Any idea what could cause this?

Not really, Volvo’s can be “quirky” on electronic issues. As they get older they get ever more quirky. It seems you had a power surge of some sort that triggered a “safety shut down” of some circuits. If they all came back, turning the car off and then back on “reset” something in the PCM. This event will likely happen again, and with more frequency. When a total failure occurs you will likely be able to track down a faulty sensor somewhere. Since you have an error message that sensor might just be in the airbag deployment or another of Volvo’s complicated safety systems.

The model year and miles on the Volvo might give a clue. If you are talking about an '01 era XC90 you are doing pretty good if this is your only problem with the car.

Sounds silly but have a the battery/charging system checked. Very simple thing but errant voltage can cause the exact symptoms you have.

I thought my Acura MDX was possessed with nutty electronics and a simple $100 battery fixed it. It included check engine light, AWD failure, air bags off due to low voltage message(clue).

My wife’s Subaru Legacy went nuts similar and it turned out to be a faulty voltage regulator on alternator. So we replaced entire alternator and back in business.

The trouble may have been caused by the ACC contacts of the ignition switch. They usually provide power to the accessories you mentioned.