When was the last time you lubed the deck? This is the first thing to try, do attempt to tighten the deck first, this would only make it worse...
Do to your local fitness equipment store and get some lub and apply liberally to the deck.
Is that only after it has stopped or do these not work before you stand on the unit?
Then you need to dismantle the unit and check all connections, check between the console and the motor control board as well as the motor control board to the incline motor