lawnboy selfpropelled,model 10694?

my mower is 5 years old, and I've had no problems so far, the first time i mowed this year it started and ran just fine but the next time i went to start it, as soon as the chock shuts off the motor stops, can any one give some kind of idea what to check. I check the spark plug, gas, screen in the tank, what do I do next ?