The steps for getting the runner up and running (and surviving reboots) should be something along the lines of:

1. Download the runner
2. Register the runner
3. Install the runner and service with:

gitlab-runner install
gitlab-runner start

The machine should now be ready to serve as a runner, and nothing else needs to be done to it (until you want to update the runner...).

Should register be called once or every time I reboot the system. What about install and start?

Register should be called once, this creates a config.toml file which saves the configuration of the registration across reboots. The files location changes depending on how it was registered. IE on Linux, registering a shell runner with sudo, would save the config.toml file to /etc/gitlab-runner/config.toml.

With regards to install and start, also only needs to be run once and survives across reboots. The install installs the GitLab Runner as a service, and start just runs it the first time.

To restart a runner should I do stop , uninstall and then install start run?

Just do a gitlab-runner restart.

Should I have to run it or start would have the same effect?

If you have done an install and start you have no need to use run. I believe run is only for one use (on the open terminal) for debugging jobs. start is for the service on the machine.

HTH.