97 240sx se transmission

[MB97KA240sx]

97 240sx se AT trannyI used Overdrive just when going on the highway and hit O/D off when in town driving. A while ago it started turning on and off by itself. Its been a few months and i just run it with O/D on all the time and its fine. I tried turning it off a couple times since but it doesn't work. The light will come on sometimes when switching from park to reverse, neuteral, and drive. but ussually will go off once it starts going. Is the switch shot, a solenoid, or something different? The light works because it comes on when the car starts.

thanks for any advise