Reset the "Start" button, ensure the dryer knob is not positioned between settings and make sure the dryer door is completely closed. Verify that electricity is running to the appliance.
Give your dryer a half-hour break and reduce the amount of clothes in the drum. Keep the drum no more than half full, which will put less stress on the motor.
Clean out your lint trap and remove any hard items around the edge of the drum. The problem could be as simple as some loose change getting stuck inside.
Increase the amount of electricity that is powering the drum. The circuit should be pumping 240 volts of power into your dryer for optimum performance.
Check for blockages in the exhaust ducts and other ventilation pipes, which may be affecting the drum.