Almost always a jam. Food debris (usually fibrous vegetable matter, chicken bones, or fruit pits) has become wedged between the impellers and the grind ring, preventing the motor from rotating. The motor tries to turn, overloads, and trips its internal thermal reset.
Homeowner fix: turn off the disposal, wait 5 minutes for the thermal reset to cool, use the hex wrench supplied with most disposals (fits into a hex socket on the bottom of the unit) to manually turn the impellers and free the jam. Reach in with tongs or pliers (never with hands) to remove the debris. Press the red reset button on the bottom of the unit. Try running the disposal with cold water.
If the jam is beyond DIY reach, professional service can clear it and inspect for internal damage. Jam clearing is a $95 fix with the diagnostic waived.









