It is not Soler's. I also do not think that it is Scarlatti; I'm very familiar with Scarlatti's Sonatas, even most of the obscure ones. But it's possible. Where, exactly, did you get like, just the first bar of a piece, and then a random passage from the middle of it? Like, are you transcribing this by ear, or do you have unmarked sheet music? Is "Andante-Moderato-Lento" actually part of the score? If so, it is 100% not Scarlatti, and like I said, it is not Soler.