Dought & clear, - Sending blessings upon the Prophet (blessings and peace of Allaah be upon him) when he is mentioned in obligatory and naafil prayers.

If a person recites a verse whilst praying in which there is mention
of the Prophet (blessings and peace of Allaah be upon him), should you
send blessings upon him because of mentioning him, or is sending
blessings upon him not among the actions of prayer except at the
appropriate point in the Tashahhud, so it should only be done then and
not at any other point?.
Praise be to Allaah.
In the obligatory prayer, that should not be done, because there is no
report of that from the Prophet (blessings and peace of Allaah be upon
him). But in the naafil prayer, there is nothing wrong with it,
because when he (blessings and peace of Allaah be upon him) prayed
tahajjud at night, he would pause at every verse in which Allaah was
glorified and glorify Him, and at every verse that mentioned seeking
refuge with Allaah and seek refuge with Him, and at every verse that
mentioned asking and ask of Him. Sending blessings upon him (blessings
and peace of Allaah be upon him) falls into the same category.
And Allaah is the source of strength. End quote.
Majmoo' Fataawa al-Shaykh Ibn Baaz (11/201)