Q. If someone goes to sleep for a short time on the night of Shavuos should he say the brocho of Hamapil?
A. Shaarei Teshuva, Birkei Yosef (O.H. 229: 2) and others maintain that if one goes to sleep before daybreak, the brocho of Hamapil should be recited, although some Poskim disagree, when one goes to sleep after chatzoz. (See Nitei Gavriel 17: 1).
Horav Shlomo Miller’s opinion is that he should recite even if he takes a nap longer that a half an hour, before daybreak.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller Shlit’a