She was concentrating on her book and his voice startled her. The noise of the car startled the birds and the whole flock flew up into the air. Her article on diet startled many people into changing their eating habits.
for no apparent reason: Emma suddenly blushed for no apparent reason. all too apparent: The potential for loss of life was all too apparent. it becomes apparent that: It soon became apparent that the two women knew each other.
to be on tenterhook
We were on tenterhooks all morning waiting for the phone to ring.