Compressors can make a rattling noise, when the mechanism inside the compressor gets out of balance. Compressors shake when they shut off, due to the sudden stop of the pressures that have been built up. That's why they are mounted on rubber grommets. After awhile the mechanism can get unbalanced and the compressor can rattle when it quits and be louder then normal while it's running. This is normal and does not affect the compressor. It does not mean it's going out. Depending on the age of the unit, the compressor can get hot. For specific information about your freezer, you can resubmit your question with more details and please include a complete model number.