Like a deer in headlights

Origin

In the early 20th century, as automobiles became common and roads extended into previously remote areas, motorists began to observe a peculiar phenomenon: deer, illuminated by the bright beams of headlights at night, would often freeze in place rather than flee. This momentary paralysis, a survival instinct overwhelmed by intense, unexpected light, quickly became a vivid and common sight. The striking image of an animal, caught motionless and wide-eyed by an oncoming threat, soon entered the lexicon as a compelling metaphor for human surprise, fear, or confusion, capturing that instant when action gives way to stunned immobility.