Cook, If the unit is new to you then I agree with full time dad, almost all jiffy owners I know stand the unit upright, then open the vent screw 1 turn on the gas cap then start and drill. However if you've had the unit awhile and it has'nt given you any trouble, check the spark like fishman said, make sure you are ready to ck. spark right away after it quits. (could be a bad or overheating coil).
Also make sure your blades are sharp if you need to push down on the auger to make it cut that's needless wear on the motor and may cause part of the symptom you describe. Let us Know how you make out! trapper