How to restart the engine again? (libido)

1. Don't fap until you have recovered from your addiction fully.
2. Your libido should come back by itself sooner or later, so you don't necessarily have to worry about manually restarting it.
3. Depending on your goals and how prone you are to developing addictions, controlled masturbation after full recovery can be okay, but should imo be done because you actually feel like doing it, and not for some weird sense of responsibility to restart libido. It's okay to have time periods when you just don't feel like doing anything sexual. You could use that time to find some other content to your life.