I gather you are not taking the trazadone? If you are, that may well be the culprit. Trazadone is frequently prescribed as a single dose in the evening before bed to induce sleep. Depending on how much you are taking when, if at all, it might be worth discussing that with your pdoc ... Zoloft could be unrelated to the sleepiness, or you may still be staging on to the drug and experiencing an early side effect, or it is augmenting the effect of trazadone.

Good luck.