Transitive starten is only used as “cause to run/move/proceed” (in a concrete or figurative sense). Possible objects of starten are machines, missiles, operations, projects, events, etc. The verb cannot be used in the sense of “begin to do”, for example in a sentence like: “He started smoking.” For this see anfangen and beginnen.
intransitive, auxiliary sein to startrace car, airplane, etc.Die Maschine ist pünktlich gestartet. The plane started on time.
transitive, auxiliary haben to start somethingIch habe den Computer gestartet. I've started the computer.