Odd Signal Indicator Behavior

[palallin]

This is a new one on me. while driving home last night, my truck's right turn signal indicator flashed randomly on the dash. It was intermittent, sometimes remaining on a few seconds, other times flashing rapidly or slowly. There were long periods when it was not lit at all.

So far as I could tell from the driver's seat, there was no corresponding odd behavior of the actual signal lights, front or tail.

Any ideas where I might begin to look?