afraid of one's own shadow
Very timid and fearful, as in Richard constantly worries about security; he's afraid of his own shadow. This hyperbole has been used in English since the early 1500s, and some writers believe it originated in ancient Greece.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.