Aside from the overbearing sense of familiarity, Starscream also picked up on a creepy sort of vibe. Which was probably from the fact that he apparently actually believes in Primus and Starscream knows first first hand that you can't trust religious zealots.

The way this mech held himself, the confidence and just stature. He just had this feeling. But it was one that Starscream didn't particularly care for.

Either way, he didn't move from his spot and just eyed the larger Decepticon.

"Starscream. I assume that if you're of any importance, you might have heard of me."