Question: There are those that kiss their Tzitzis during Shema at Shacharis as per Kitzur Shulchan Aruch 17:7 and the Kaf HaChaim 18 and there are those that do not. What is the source and reason for those that do not kiss their Tzitzis during Shema at Shacharis?

Answer: 
Ma'ase Rav Siman 39 says that the GR"A would not kiss his Tzitzit during Keriyat Shema. The Kovetz Mepharshim (printed on the side in the [Weinrab edition](http://www.google.com/imgres?um=1&hl=en&sa=N&biw=1280&bih=699&tbm=isch&tbnid=SGjK79JsFGdFjM%3a&imgrefurl=http://www.mysefer.com/product.asp?P_ID=4461&strPageHistory=related&docid=xc8pmsi4GkM_rM&imgurl=http://www.mysefer.com/uploads/images_products/4461.jpg&w=150&h=225&ei=tSUzT6_kFaPC0AHQwM30Bw&zoom=1&iact=hc&vpx=680&vpy=213&dur=1311&hovh=180&hovw=120&tx=82&ty=101&sig=106136706347559917116&page=1&tbnh=162&tbnw=108&start=0&ndsp=22&ved=1t:429,r:4,s:0)) supposes that he did so because he held that when saying the third paragraph of Keriyat Shema one should gaze at his tzitziyot (see biur hagra O"H on Siman 24 seif katan 8), and kissing them breaks his focus.
I have not the exact halachic sources but read that some poskim considered those kissings during the shema as hefsek, for example : The Vilna Gaon, Chazon Ish, The Steipler, Rav Moshe Feinstein (read there : <https://halachafortodaycom.blogspot.com/2012/04/q-page-1.html>)

Also I read once that some don't even grasp their tzitzios during shema like for example Rav Chaim Soloveitchik but that's an other subject.