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.
Check your run capacitor 2.5,5,7.5, a big one might be ten uf. If that's good check to see if it is wired into the auxiliary contacts of your compressor contactor. If it should be and isn't. Try adding it in ( if your auxiliary is normal open" Then see if there is a fan cycling switch on the high side. Perhaps it isn't making like it should. Put a meter on the switch and check for continuity once your pressures go up.