listlessness

noun

1. A deficiency in mental and physical alertness and activity: dullness, hebetude, languidness, languor, lassitude, leadenness, lethargy, sluggishness, stupor, torpidity, torpor. See action/inaction.
2. Lack of emotion or interest: apathy, disinterest, impassivity, incuriosity, incuriousness, indifference, insensibility, insensibleness, lassitude, lethargy, phlegm, stolidity, stolidness, unconcern, uninterest, unresponsiveness. See feelings.

The noun has 2 meanings:

Meaning #1: a feeling of lack of interest or energy
  Synonyms: languor, lassitude

Meaning #2: inactivity resulting from torpidity and lack of vigor or energy
  Synonyms: torpidity, torpidness, torpor