ürpermek = to chill, to tremble if a wind blows and you chill...

ürperti (noun) is the “feeling of tremble, creep or chill” . However it is not like “shaking because of cold”. You can also associate it with the word "horripilation". “ürpermek” is the verbal form of it. “ürper” is the stem. (Eğer) Bir rüzgar eser de ürperirsen,...... - if the wind will blow and you will tremble/creep,.... (Please correct the English part if it needs) Here, "de" is conjunction. This structure makes the 2nd sentence (ürperirsen) the consequence of the 1st sentence (Bir rüzgar eser). Namely, “you feel tremble as a result of the blowing wind”. ürper-ir-sen is the conditional form of ürpermek. Here "-ir" notifies the "future event". "-sen" is the part that is making the sentence conditional ben ürperirsem sen ürperirsen o ürperirse biz ürperirsek siz ürperirseniz onlar ürperlerse