It is probably the drain pump that is running. It will do that if water has leaked into the base tray & activated the flood switch. Pull dishwasher out from under bench. Tip it back as far as you can & see if water comes out (have some old towels ready) Once water is out it should come back to normal. If the same thing happens again you will need to find out where it is leaking from. It may not come back.
Lincoln Appliance NZ, November 2016