intermittent 4 way flashers while driving

While on a long trip, about 3 1/2 hours into the trip, driving at highway speeds (65 - 70 mph), not touching any controls... The 4 way flashers started to flash. They flashed 5 times. Then about 1/2 hour later they flashed again. This time they flashed 3 times, paused 2 seconds, flashed 2 times, paused 2 seconds, and then flashed 3 times. No other indicator lights came on, and I didn't notice any other "electrical" issues.

I have only had the truck (08 crewcab automatic 4X4 "base model") for 2,000 miles. Total miles is 5,000 (bought used after a repo)

The flashing happend about 500 miles ago, and hasn't happened since.

Any ideas?