madcap, change, unprompted, bizarre, hotheaded, unpredictable, flaky, outre, impetuous, freakish, fantastic, outlandish, mercurial, continue, driving, study at inconstant, off-the-wall, surprise, brainish, unstable, ticklish, fantastical, unsteady, tearaway, freaky, flakey, gonzo, temperamental
capricious (part of speech: adjective)
irresolute (part of speech: adjective)
insipid, undecided, shrinking, changeable, inconsistent, spineless, fly-by-night, shifty, infirm, shy, unresolved, irresponsible, unwilling, undependable, double-minded, tentative, irresolute, uncertain, dillydallying, weak, watery, unsure, yellow, shilly-shally, halfhearted, erratic, hesitant, vacillating
motiveless (part of speech: adjective)
careless, chancy, reasonless, flighty, fleeting, haphazard, ambivalent, indecisive, irregular, systemless, whimsical, motiveless, fickle, sporadic, nonsystematic, flitting, wandering, fanciful, rambling, spastic, unmethodical, volatile, wayward, random, adrift, impulsive, arbitrary
irregular (part of speech: adjective)
- At such times he never succeeded in remembering that she was but little more than a child, heart- free, capricious, and wilful. - "Amarilly of Clothes-line Alley", Belle K. Maniates.
- " I know he's a bit capricious and exacting at times. - "Calvary Alley", Alice Hegan Rice.
- There are amateur collectors who know more about book- binding, than even certain good workmen; but there are also others, of a capricious taste, who are rather likely to lead half- instructed workmen astray, than to put them in the proper road. - "A Bibliographical, Antiquarian and Picturesque Tour in France and Germany, Volume Two", Thomas Frognall Dibdin.