Should one stand while reciting the morning blessings [i.e. Birchas Hashachar]?
Letter of the law: From the letter of the law, one is only required to stand when saying blessings which involve commands, such as when saying the blessing over Tzitzis, and Tefillin. However, blessings of praise do not require standing. This especially applies to Birchas Hashachar which were initially instituted to be said in the process of awakening, and hence many were said in a sitting or lying position. [Thus, in the morning blessings, from the letter of the law one is only required to stand for the blessings of Al Netilas Yadayim and Birchas Hatorah being that they are commands and not blessings of praise, however he is not required to stand for any of the other morning blessings.] Nevertheless, some Poskim argue and rule one is to stand even for blessings of praise.
Custom: Practically, the custom amongst Ashkenazi Jewry is to say all the morning blessings in a standing position. However, Sephardic Jewry is accustomed to sit while reciting the blessings in order to increase concentration.
One is only required to stand for the blessings of Al Netilas Yadayim and Birchas Hatorah. Nevertheless, the Ashkenazi custom is to stand for all the morning blessings. However, the Sephardic custom is to sit while reciting the morning blessings.
 Admur 8:3; M”A 8:2; Beis Yosef 8:1 in name Orchos Chaim Tzitzis 27 based on Yerushalmi “That which it states in the Yerushalmi that all blessings are to be said standing, it refers to Birchas Hamitzvos”; Haittur Zohar Tetzaveh brought in P”M 8 M”Z 1; P”M Pesicha to Hilchos Brachos 202:18 “We hold that Birchas Hamitzvos must be said standing” [however, see P”M 432 M”Z 3]; M”B 8:2 “All blessings of Mitzvos need to be done standing”
The reason: This is learned from Sefiras Haomer which is required to be said and blessed on in a standing position. [M”B ibid; See Kol Bo p. 16, brought in P”M 432 M”Z 3]
Cases of exception: The above rule is with exception for the blessings made over Shechitah and Challah, being that these two Mitzvos don’t hold the same weight as other commands, as they are done merely for the sake of being able to eat food. [Admur ibid; M”A 8:2] Vetzaruch Iyun according to this ruling here why we are accustomed today to sit by various blessings of Mitzvos, such as “Al Achilas Matzah”; “Leishev Basukkah” and others. See P”M Pesicha to Hilchos Brachos 202:18 who explains that since these Mitzvos involve eating, they may be said in a sitting position; See Bach 8; Pnei Yehoshua Megillah 21a; Mor Uketzia 8; Piskeiy Teshuvos 8:4 who differentiate between Mitzvos that are performed standing versus sitting.
Other opinions: Some Poskim rule that the blessings of Mitzvos are not required to be said in a standing position, with exception to those Mitzvos that must be performed standing. [P”M 432 M”Z 3 “Chazal instituted the blessing similar o the performance if it is done standing”; Artzos Hachaim 8:1 states it is only a Mitzvah Min Hamuvchar; Bach 8 only requires standing for Mitzvos that have no benefit; See Pnei Yehoshua Megillah 21a; Mor Uketzia 8 that depends it if the Mitzvah is accustomed to be performed standing; Piskeiy Teshuvos 8:4]
 P”M Pesicha to Hilchos Brachos 202:18 “Blessings of praise may be recited in a sitting position, except for Birchas Halevana”; P”M 432 M”Z 3 “Birchas Hanehnin may be said sitting and its possible that this applies likewise to blessings of praise”; Implication of Rambam Brachos 10:17; Abudarham Dinei Birchas Hashachar p. 45; Birchas Habayis 1:78; Piskeiy Teshuvos 218:1; 227:5
 See P”M Pesicha to Hilchos Brachos 202:18; Admur 46:2
 So is understood from Admur and Poskim in previous footnotes, as one is obligated to wash hands in the morning upon awakening. This is unlike washing for bread if which its blessing may be said in a sitting position. [See Admur ibid; Piskeiy Teshuvos 158:2; Seder Netilas Yadayim of Rav Elyashvili footnote 47 that so was custom of Rebbe]
 So is understood from Admur and Poskim in previous footnotes, as one has a constant obligation to learn Torah and so is the custom of Jewry; See Maarah Kohen 3:3; Yaskil Avdi 8:3 that this is similar to the standing of Bnei Yisrael on Har Sinai.
Other Opinions: Some Poskim rule that Birchas Hatorah may be said while sitting. [Aruch Hashulchan 47:7 and Rameh 102; Beir Moshe 5:17 [see there for a lengthy discussion on this matter]
 Siddur Yaavetz “I must teach you the following rule: All blessings of praise and thanks are to be said in a standing position”; See Piskeiy Teshuvos 218:1
 This is done to suspect for the Yaavetz ibid who rules that all blessings of praise of Hashem are to be said standing. This is especially understood from the fact that the 18 blessings of Birchas Hashachar correspond to the 18 blessings of Shemoneh Esrei as explained in Shaar Hakolel 1:6-11.
 Kaf Hachaim [Falagi] 9:7 “One is not to recite Birchas Hashachar while getting dressed…rather he is to sit in his place in seclusion and concentration in order to say Birchas Hashachar”; Yechaveh Daas 5:4