Sets of three beeps means key out of range.
However, you should see a warning message on the dashboard if that happens.
Something like a picture of a key and the words: "Key not detected"
If the battery in your keyfob is near replacement, or you have something else in your pocket blocking the signal, I can imagine that warning firing off randomly.
If your digitiser issue is effecting the dashboard, so you don't get any messages, you could try put the fob into the fob slot (in the centre of the dashboard, near the cigarette lighter) and see if that stops the warning tones.
If that works, it's time to replace the battery in the fob.