Saturn transmission issue

Make: saturn
model: 4 door coupe
year:1993
engine: 1.9 L4 tbi
transmission: automatic
mileage: 100,000

It seems like a strange problem. I'll be driving along and the check engine light will come on then the car will not shift gears until I turn the ignition off then restart the car. At this point the car is back to normal, shifts fine ect. Then a little while later the check engine light will come back on and transmission wont shift till I turn the car off and restart it.

Have any ideas as to what may be causing this?

Thank you,

Guy Williams