This could be because of the phenomenon that the internet has coined as "resting bitch face." Ty Tashiro, psychologist and author of the book "Awkward: The Science of Why We're Socially Awkward ...

He’s got this look on his face at all times that I just call resting bewilderment face.” Reenacting the expression by widening his eyes and opening his mouth, Pratt said, “He’s like this.