Or search: phlegm, torpor, inertia, languor, flatness, slackness, inanition, torpidity, inactivity
2 Syllables: SU
every, feathery
3 Syllables: SUU
beggarly, Beverly, Chesterfield, cleverly, energy, evergreen, jeopardy, leathery, reverie, treachery, treasuries, treasury, westerly, yesterday, yesterday's
4 Syllables: USUU
accessories, accessory

Found 19 words across 3 groupings. Skipped 2 excess words of a similar stem.