The Laws of Prayer /The Blessings of the Shema (75)

1. One who is reciting the Shema should not make signs with his eyes or motions with his lips or fingers during the first paragraph, which is the main part of accepting the yoke of heaven, as if one does this, it is considered reciting in a makeshift way. Even for a good deed one may not make signs. (Kitzur Shulchan Aruch 17)

2. Some are stringent and insist that even during the second paragraph one may not make signs etc. In this case, however, everyone agrees that for a Mitzvah one is allowed to. (ibid)