Can you provide us with the model you have.
If the heating element is actually working, and then the smoker is shutting down; it may be a faulty temperature sensor. It may need to be replaced, but in the meantime it is possible that it is stuck open, sometimes holding an ice cube on the sensor for a few minutes may reset it. Usually you can locate the sensor by looking inside the smoker, and you will see a small disk the size of a quarter.