When it tries to run, does the compressor hum and then go off with a click a few seconds later.
Does it then repeat this every so often.
OK, thanks for that.
This normally happens when the compressor is faulty and/or has jammed.
It heats up extremely quickly and trips the overheat protection.
As it cools down, it tries to start again and trips the protection again.
Unfortunately this normally requires a new compressor and a regas.
You would be looking at an expensive repair I'm afraid.
You need a refrigeration engineer to change the compressor and regas the system.
I'd guess at least £150 but more likely around the £200 mark.
Sorry, not good news or an easy fix.
I wish it was as simple as pressing a few buttons.
Hope this is of some help
Let me know how it goes or if you need more help
No, the thermistor won't cause this.
I think it's unlikely to be a faulty starter relay.
However, if you unplug the appliance and take the cover off the box attached to the compressor you can take out the assembly and check to see if it's failed.
Good luck with it, let me know what you find.