Q: When I start the car it works good hold light is blinking gear takes long to turn then I randomly lose power,like am in 3 gear

When I start the car it works good hold light is blinking gear takes long to turn then I randomly lose power,like am in 3 gear other then that works good on the high way no prob I carried it to scan and there was a prob with the shift solenoid I change that already I don't know what to do can you help me
My car has an automatic transmission.