DIAGNOSIS You likely have the thermostat dial set to the wrong position for the ambient temperature, or the fridge is in a space that's too hot. These units run a lot if set up incorrectly.
FIX First, check the thermostat dial. Turn it to a medium setting (around 4 or 5). Don't crank it to Max/7 immediately. Let it run for 24 hours to stabilize. Ensure the fridge is in a room under 90°F, with at least 4 inches of clearance on all sides for airflow, especially the back.
IF THAT DIDN'T WORK The door seal might not be sealing. Test it by closing the door on a dollar bill; if you can pull it out easily, the seal is weak. Clean the gasket with warm water and check for any warping. A poor seal makes the compressor run non-stop.
HEADS UP It's normal for a new fridge to run almost continuously for the first 6-12 hours as it pulls down to temperature. Give it a full day before panicking.