starti

The fence is the whole point of this word. Komenci is to begin, in general, and it is transitive: you begin something. Mi komencas la laboron. For the intransitive you add -iĝ-: la laboro komenciĝas, the work begins. Starti is intransitive already, and it is narrow: it belongs to races, engines, vehicles and departures. A runner startas. A car startas. A meeting does not starti, it komenciĝas, and using starti for it marks you as someone translating from English word by word.

Register: sport and machinery, not general prose. Starto is the start of a race and the starting line; startloko the starting position; startilo the starter motor; startigi is to start something else off, which is what you do to a stubborn engine. Aviation borrowed it too, though ekflugi is the better word for taking off, and computing uses lanĉi or ruli for starting a program rather than starti.

Watch the one-letter neighbour. Stari is to stand and has nothing to do with this word. Li staras he is standing; li startas he is off. In writing the difference is a single t; in speech it is clear enough, but it is worth being deliberate about the first few times.