a sleepwalk

a sleepwalk

Something that is done without much or any effort, thought, or skill; a cakewalk. I've been running marathons for years now, so this 5K run will be a sleepwalk for me. I knew I wouldn't have too much trouble in the entry-level computer class, but I wasn't expecting as much of a sleepwalk as that!
See also: sleepwalk
Farlex Dictionary of Idioms.

sleepwalk

n. a movement toward something without effort; easy advancement; an easy task. (see also cakewalk, walk.) Getting the degree was a sleepwalk. Getting a job was hell.
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions
See also:
  • sleepwalk
  • cakewalk
  • a walk in the park
  • walk in the park
  • walk in the park, a
  • park
  • lead-pipe cinch
  • be (one's) man/woman
  • be somebody's man/woman
  • (as) easy as duck soup