My Automatic transmission slips while driving and will not downshift to 1st gear at the light unless I shut it off and restart the engine. I think it may be a bad ECM (Engine Control Module).
Are you telling us… or asking us? Here is a wild guess since you didn’t tell us ANYthing about the car. Not the mileage, nothing. Since it is a GM H platform, it has a 4 speed automatic and a 3800 V6 most likely… guessing since you didn’t tell us.
Your transmission needs to be rebuilt.
Does this car have OBD2 diagnostics? '96 is when all cars did but some got it earlier. If you can communicate with the ECU, it is likely OK.
Have you tried to pull trouble codes? If it is an OBD1, and the ECU responds with 12, the ECU is likely OK.
If your 95 GM vehicle has the 16 pin non-compliant OBDII connector, it requires either a factory level scan tool or an special cable along with the software to pull codes.