Grant, we pray, that we may feel her to [be] interceding for us

. . . grant, we pray, that we may sense [(sentiamus)] her to [be] interced[ing] for us, through whom we were found worthy to receive the author of life, our Lord Jesus Christ your Son.

"Deus, qui salutis aeternae beatae Mariae virginitate fecunda humano generi praemia praestitisti, tribue, quaesumus, ut ipsam pro nobis intercedere sentiamus, per quam meruimus auctorem vitae suscipere, Dominum nostrum Iesum Christum, Filium tuum."

". . . grant, we pray, that we may experience the intercession of her, through whom we were found worthy to receive the author of life, our Lord Jesus Christ your Son."

     Collect for the Solemnity of Mary, the Holy Mother of God, Roman missal.  This is Bruylants, vol. 2, no. 440 (on p. 122), which he traces back to the Gelasian sacramentary of the early 8th century. =Corpus orationum no. 2113b.  Cf. Corpus orationum no. 2113a, which begins as follows:

Deus, qui spe[m] salutis aeternae beatae Mariae virginitate. . . .

See also Cuthbert Johnson & Anthony Ward, The sources of the Roman missal (1975) I:  Advent, Christmas (Notitiae 240-242 (Rome, 1986)): 213/653-214/654.
     Sentiamus (that one form alone) occurs twenty times in the current Roman missal.