Normal Refrigerator Cycle Times
It is normal for the refrigerator motor to stop during the defrost cycle and while in this mode, no matter where you set the thermostat, the compressor will not come on. The motor will start again upon completion of the automatic defrost cycle (in about 35 minutes). It is also normal for the compressor to start and stop often as the temperature control tries to maintain even temperatures (much like an air conditioner's thermostat).
The refrigerator may run 75% - 90% of the time, and in hot, humid areas, may even approach 100% run time.