Most transformers seemed to have human friends either being very timid/skittish all the time at that. Optimus doesn’t have one since he never felt the need, but bit the bullet and gave into the trope of Autobots having human companions.

Optimus: “So.. do I wait or go up to one or…? I’m afraid I do not know how this works.”

Optimus would ask Bumblebee. Though Bee couldn’t verbally speak he used his car radio as a substitute and explained how he managed to befriend Sam Witwicky.