The poskim are divided as to whether sleep is considered a break after which it is necessary to repeat the recital of Birkot HaTorah.
According to most Rishonim, among them the Rosh, a person’s regular sleep in his bed is considered an interruption regarding Birkot HaTorah. The whole time a person is awake, the Torah continuously escorts and guides him. However, when a person sleeps, he ceases to think and his consciousness fades. Therefore, sleep is deemed an interruption regarding the mitzvah to learn Torah. Based on this, it is necessary in principle to recite Birkot HaTorah even after a nap during the day. Nonetheless, it has been customary to consider daytime sleep, even if it lasts a long time, to be temporary sleep, which does not constitute an interruption; hence, Birkot HaTorah recited in the morning are also effective after a daytime nap. However, regular sleep at night is an interruption and one must recite Birkot HaTorah after it. Therefore, one who needs to arise in the middle of the night for guard duty, and intends to return to sleep afterwards, recites Birkot HaTorah twice, once when he wakes up for guard duty, and a second time when he wakes up in the morning. That is the practice of Ashkenazim and many Sephardim (Shulchan Aruch, Orach Chaim 47:11; Mishnah Berurah 29).
There are those who say that sleep is not considered to be an interruption concerning Birkot HaTorah and that the law of Birkot HaTorah is similar to the law of Birkot HaShachar, which are recited once a day. Therefore, one who wakes up in the middle of the night for guard duty recites Birkot HaTorah after the first waking and does not recite them after the second time he wakes up (Kaf HaChaim 47:29; concerning the laws of Birkot HaShachar see earlier in this book 9:5).
The opinion of the Ben Ish Chai, Vayeshev 13, also cited by the Kaf HaChaim 47:29, is that, according to Kabbalah, the law of Birkot HaTorah is similar to the law of Birkot HaShachar, that they are not recited twice in a 24-hour period. Their opinion is based on Rabbeinu Tam. However, according to Rabbeinu Tam, Birkot HaTorah are recited in the morning adjacent to Shacharit, and according to the Ben Ish Chai, if one slept twice at night, he recites the blessings after the first sleep and not after the second (and he should have kavanah in Ahavat Olam to fulfill the obligation of Birkot HaTorah). According to this, there is a certain distinction between Birkot HaShachar and Birkot HaTorah. Birkot HaTorah has two intentions: one, as part of Birkot HaShachar whose time starts after chatzot, and the second, as berachot before learning Torah. Therefore, one who wakes up close to chatzot should wait and recite Birkot HaTorah with Birkot HaShachar after chatzot. Yet, if he wakes up long before chatzot, he may recite them before chatzot alone. There were devout people who were accustomed even in such a case to wait and recite the blessings after chatzot.