Automatic workflow execution

I'm developing a personalization, but I need the stages of a workflow to be executed automatically in all its stages, for example. my flow consists of a start, activity 1, activity 2 and released. I need each stage to be executed automatically by the server without a user releasing the activity I need you to spend 20 days before reaching stage 1, once we reach stage 1, send an email as it normally is to a user. before reaching stage 2, you must wait 20 more days, when these 20 days expire you reach stage 2, and the same for the liberated stage. I need these stages of my workflow to be executed automatically without the need for the user to have interaction in myinbasket Is there something like that?