Electronic Shift Control Problem! Need Help!

[chll69]

I have a 1992 325i; E36, i recently have been having a problem with the electronic shift control. Every once in a while the light appears on the dash and the car drops into 3rd, and stays there for the duration of my drive. After turning the car off and coming back to it, the light does not appear and things are back to normal, any idea why it might be switching on and off???? any help is appreciated, Thanks alot!