1) check the motor bearings. Do this buy spinning the fan blades with the DISCONNECT OFF. Is it making a noise? Does it feel like metal on metal?
You can also see if shaft seems to wobble while spinning.
If bearings are bad replace motor.
2) most likely that loud sound is your compressor. Refrigerant migrates into the oil while the system is off. When your crank case heater goes out it may sound rough for a minute while the oil heats up and the refrigerant is boiled off the crank case oil. Check this and get back to me.
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