Diagnosis
Random triple beeps are almost always a door alarm. One of the doors (fridge or freezer) isn't closed completely, or the sensor that detects it being closed is acting up.
How to Fix It
First, rule out the obvious. Open and firmly close both the fridge doors and the freezer drawer. Listen for a solid *click* and make sure nothing inside (a butter tub, a milk carton) is blocking the door from shutting all the way. If the beeping stops, you found it. If it continues, you need to check the door switches. These are little plunger buttons in the door frame that get pressed when the door closes. The one for the right fridge door is a common troublemaker. Unplug the fridge, then locate the switch for the problematic door. You can test it by pressing and releasing the plunger while listening for a faint click. If it feels mushy or doesn't click, it's likely failed and needs replacing.
If That Didn't Work
If the switches seem fine, the wiring to them or the main control board interpreting the signal could have a glitch, but that's less common than a simple bad switch or an ajar door.
Heads Up
Sometimes, especially on uneven floors, the fridge can settle in a way that makes a door *almost* close but not latch. Use a level on the top of the fridge from front to back and side to side. If it's off, adjust the leveling feet at the bottom front corners.