When kissing tzitzis during kriyas Shema, is not considered a hefsek to stop in the middle of a sentence and kiss the tzitzis?
It is not considered a hefsek, because he is not taking out and saying unrelated words. There are instances when we should not make a hefsek in time. such as between the bracha of גאל ישראל and Shemona Esrei, or between the words of the bracha and eating, however that is only applicable when two items are meant to be done together, which doesn’t apply here.
gmar chasima tova