> Try not to move it much as the coolant doesn't like being disturbed hence why you are told to let it stand before switching on when new
Also clean any dust accumulation ( carefully)off heat exchanger grill thingies on the back.
After trying all these sensible suggestions above, as a last resort, switch it off, turn it upside down for a day, turn it upright for a day, switch back on.
This has worked successfully for me at least twice, getting several more years use out of apparently knackered fridges.