once bitten, twice shy
One is cautious if one has been hurt in the past.
VERBS
be, feel, look, seem, sound
She felt shy when the teacher asked her to speak in front of the whole class.
become, get, go, grow
ADV
desperately, excessively, extremely, painfully, terribly, very
My younger brother is desperately shy and always hides behind me when meeting new people.
all
When the teacher asked him to read aloud, he went all shy and stared at his desk.
almost | a bit, fairly, a little, quite, rather, slightly, somewhat
naturally
My daughter was naturally shy as a child, but she became more confident in high school.
chronically
PREP
of
My younger brother felt shy of speaking to the new teacher on his first day.
with
She felt a little shy with the new students in her class at first.
ADV
violently
PREP
at
The nervous dog shied away at the sudden loud noise from the fireworks.