Docker Course, start command not working

I have been trying to run
docker start -i container-id
for like 20 min and i cannot get docker to run an interactive shell on a container that already exists.
docker run -it ubuntu
creates a new container, runs it, and attaches a shell to it, just like it says it will in the course but i cannot interact with that container once i exit it and try to start it again

Did not use Docker for a while but AFAIR you don’t need to specify -i if you did when you created the container.
try docker ps -a to list your containers.
Then docker start {container_name| container_hash}