While driving,the dashboard suddenly showed the "Check Air Suspension" message along with an audible alarm. When the car was stopped and engine shut off and then restarted, no further message appeared. The air suspension switch in the trunk showed the ON position.

What caused this message and how does one check the air suspension system?

As long as the car is not sagging or looking like there are four bodies in the trunk, I think enough time has passed to rule out a leak. I think there might have been a slight drop in pressure or just a electrical err that activated the message. Any problems since?