Or search: bayer, aspirin, anodyne, bufferin, analgesic, salicylate
2 Syllables: SU
trembling
3 Syllables: SUU
centering, entering, gentlemen, lengthening, mentioning, rendering, strengthening, tempering, tendering, venturing
3 Syllables: USU
assembling, remembering, resembling
4 Syllables: USUU
surrendering

Found 15 words across 4 groupings. Skipped 1 excess word of a similar stem.