No. Not unless you have been trained to do so - in which case you wouldn't be asking the question. There are numerous possible reasons for an oven "going through the motions" but not heating the food. It is extremely dangerous for an untrained person to try to repair a microwave oven, because it can possibly deliver a lethal electric shock, even after it has been disconnected from the mains.
In your case, there's no danger from microwaves. As it is not heating the food, there are none, but there may still be 4,000 volts at high current.
Jim Garrod, June 2008