Had several power outages right in a row last night, fridge is 20 years old but the compressor was replaced about 9 years ago. Was not making the noise until after the power outages, now when the compressor first starts you get the buzz/humm/rattle then it’s fine sounds normal. Fridge right now is running normal, no issues with cooling, not warm on the sides.
Thinking start capacitor or start relay? Maybe both? Hate to just throw parts at this, any guidance on where to start would be good.
Your refrigerator doesn’t appear to have a start capacitor. It does have a run capacitor but they don’t often fail and normally won’t makes things noisy.
Start relay, maybe but that is not very common.
Pull the refrigerator out, remove back cover.
Inspect the condenser fan motor and fan blade to make sure the noise is not coming from either of them.
Try using a long screwdriver as a stethoscope. Place handle end against your ear and screwdriver end against the compressor. Let the compressor start to see if this noise is coming from inside the compressor. If it is, likely the compressor itself is starting to go.
Noises on start up were common on weak or troubled compressors.