shawl
s is for speed
scuzz, soyuz, spitz
Bellybuttons would be the longest word I can think of beginning with a 'b' and ending in an 's'.
venusvanes
setup
shawl
stela or stele
Some five letter words starting with S are:sablesaladsalsascalescarescullscrewshirtshootshoresillyskirtslidesloopslopesmilesnailsnakesnoresorryspacespellspikespillsplitspokespookspoolspoonsportsquatstallstartStashstealsteelstickstingstinkstolestoopstorestormstovestrawstrumstuckstumpsugarsupersurgeswarmsweatsweetswift
Seta is a 4-letter word for hair or bristle starting with S.
Sincere is an adjective. It begins with the letter s.
crows, carts
Jumps
shoes, socks
Scare
sum
spotless