Dishwasher hums only, doesn't start

My dishwasher is cheap, old, reliable, but this morning it wouldn’t do jack.

Instead of starting the normal cycle, it just hums. It doesn’t fill with water, crank, or anything…just hums. When I say "hum" I mean "an electric motor trying to do something but not doing anything"-hum like if a garbage disposal were stuck. Fearing I’d burn the thing out of cause a short of some kind, I turned it off after 10 or 15 seconds. I tried later in the day – no luck.

What are the first steps in diagnosing?

Thanks to all!
Matt

Fixed. Being my own landlord is kind of cool.

Thanks!

Matt