I recently had the exact same thing on my Cuda and after about a week of it, it fixed itself. I'm sure it will come back and afford me the opportunity to chase the issue down. But from my memory and research there can be several causes. A bad/marginal bulb or socket. Poor ground anywhere in the circuit. The switch in the steering column. The blinker relay. Low blinker fluid.

I'd start by checking each bulb and re-seating them. Don't forget lights in the dash. Then go through the wiring and sockets. I'd rule out everything I could before getting into the steering column. The blinker fluid is an obvious thing to check.