Noisy Freezer

Our Bosch Fridge Freezer has recently started making a noise intermittently (sounds like a squeeky wheel that needs oiling) when the motor kicks in on the freezer.
When you open the freezer door or turn the unit off it stops and then when you close the door or turn it back on again it runs as normal.

I have pulled the unit out and had a look around the back but nothing seems obvious in terms of a fault.

The fridge and freezer are running absolutely fine, it is just a very annoying and load noise that starts up intermittently.

Any ideas as to what it might be?
😕