L’chatchilah, all the blessings should be recited as close as possible to the time one wakes from his sleep and it is not necessary to say them specifically after alot hashachar. Therefore, one who gets up before alot hashachar in order to learn Torah, to work, or for any other purpose, must recite Birkot HaShachar immediately upon waking up. However, Birkot HaShachar may not be recited before chatzot (halachic midnight). Therefore, a person who wakes up before chatzot must wait until after chatzot to recite Birkot HaShachar. If he recites them before that time, he does not fulfill his obligation (Mishnah Berurah 47:31; Kaf HaChaim 29).
One who wakes up after chatzot for a few hours and plans on returning to sleep until the time to recite Shacharit, such as a soldier who gets up after chatzot for guard duty and goes back to sleep, must say Birkot HaShachar after his main waking. If, in his opinion, his initial waking is his main one, and he considers any sleep after that similar to a nap in the middle of the day, he must recite them after the first sleep. If his second rising is his main one, he must recite them after the second rising. However, the kabbalistic custom is that as long as the first rising is after chatzot, he must say Birkot HaShachar after the first rising. If he did not say them after the first rising, then he must say them after the second.
It is the opinion of most poskim that the law regarding Birkot HaTorah is similar to the ruling for blessings recited upon the performance of mitzvot. Therefore one must recite them every time he wakes up from a regular sleep at night. Still, there are those who have the custom to recite them only after the first rising (see the laws of Birkot HaTorah further in this book 10:6).
. The Mishnah Berurah 47:30 writes that if the first time he wakes up is after chatzot, he may recite Birkot HaShachar. He did not specify whether it is preferable to recite them particularly after the first rising. However, the Kaf HaChaim 46:49 writes based on the Kabbalah, that it is best to recite them following the first waking after chatzot. One who cannot determine which rising is considered his main one should practice according to the Kaf HaChaim and recite them after the first rising.Further, it is important to note that according to the Mishnah Berurah 47:30, the berachot, Elokai Neshamah and Hama’avir sheinah me’einai are to be recited after the first rising without Shem u’Malchut (Hashem’s name), and the second time he recites them with Shem u’Malchut. However, if he recited them with Shem u’Malchut the first time, he may not go back and repeat them a second time. The Bei’ur Halachah expands on this, saying that according to the Pri Chadash they must be recited only after he finishes sleeping that night. If he recites them the first time he wakes up, he does not fulfill his obligation, and he must go back and recite them after the second time he wakes up. The Chayei Adam agrees with him concerning Hama’avir sheinah. However, Sha’arei Teshuvah and Derech HaChaim write not to repeat it after waking up the second time. Therefore, the Mishnah Berurah rules that if a person already recited them, he may not go back and say them again. Kaf HaChaim 46:49 writes in the name of a number of poskim and kabbalists that even these two berachot need to be recited the first time with Shem u’Malchut and any sleep after that is considered similar to a nap taken during the day. That is how Sephardim practice. The Ashkenazim follow the Mishnah Berurah, yet, even according to him, if they recited the blessing the first time, they fulfilled their obligation. In my humble opinion, it seems that it is better to teach both Ashkenazim and Sepharadim to recite all the berachot after the main waking, because when one recites most of the berachot with the first rising and leaves two berachot for the second rising, there is concern that he will make a mistake, either by forgetting to say the last two berachot, or by accidentally reciting all the berachot again the second time he wakes up. Therefore, I concluded above to recite all of Birkot HaShachar after the main waking and even when the first waking is the main one, a person who recites Elokai Neshamah and Hama’avir sheinah at that point has on whom to rely.According to the kabbalists, the best time to recite Birkot HaShachar for one who was awake all night is after chatzot, and Birkot HaTorah after alot hashachar. However, the Ben Ish Chai, Toldot 14, writes concerning someone who goes to sleep after chatzot, that although according to the Rashash he may recite Birkot HaShachar after chatzot before he goes to sleep, the custom is to recite them after one wakes up, as Rav Eliyahu writes in his siddur, p. 3.