autopresentarse

Can mean simply to introduce oneself, but is also used in political contexts for someone who runs for office independently, without party backing — se autopresentó como candidato independiente.

• Se autopresentó ante el nuevo equipo sin que nadie se lo pidiera. — He introduced himself to the new team without anyone asking him to.
• El candidato se autopresentó a las elecciones sin el respaldo de ningún partido. — The candidate ran in the election without the backing of any party.
• Prefiero que me presenten a autopresentarme. — I'd rather be introduced than introduce myself.

In the simple "introduce yourself" sense, presentarse alone is far more natural and common — autopresentarse is really only distinctive in the independent-candidacy political sense.