unmotivated

From un- +‎ motivated.

unmotivated (comparative more unmotivated, superlative most unmotivated)

2. Lacking motivation, without impetus to strive or excel.

   Antonyms: motivated, remotivated

   Hyponym: demotivated

4. For which there is no motive, or no apparent rational motive.

   Near-synonym: unprovoked

   an unmotivated murder