restlessness has 5 distinct synonyms spread across 3 of its 4 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
the quality of being ceaselessly moving or active
“the restlessness of the wind”
a lack of patience; irritation with anything that causes delay
Synonyms, antonyms and the broader and narrower relations for restlessness come from Princeton University’s WordNet. Full sources and licences.
a feeling of agitation expressed in continual motion
“he's got the fidgets”
inability to rest or relax or be still