terrios 5dr estate, 1.3 auto.

Hello to all, i have had this car for nearly 4 years and it has been trouble free until recently when the ;overdrive off; lamp started flashing and i found myself stuck in 2nd gear..
However after switching of the vehicle and restarting it the problem went away. That was a month ago since then the problem is returning
more and more frequently. I dont think it is a mechanical problem as there are no strange noises, and the car runs fine most of the time.

any help or info offered on this problem will be greatly appreciated.

Many thanks in advance.