Dozing with Tefillin

The Gemara cites an opinion that one is permitted to casually sleep while he is wearing his Tefillin. The Rosh asks on this from the Halacha that one is not allowed to divert his attention away from his Tefillin? He answers by quoting a Rabbeinu Yona that states it is considered diverting attention only when one acts with frivolity and lightheadedness. However, standing with trepidation in front of Hashem or being preoccupied with other things is not deemed to be hesech hada’as. The Shagas Aryeh states that this is not the opinion of the Rambam because he rules that one who is under duress is exempt from donning Tefillin because when one is wearing Tefillin he cannot divert his attention away from the Tefillin. He is not acting with frivolity and nevertheless the Rambam rules that this is considered hesech hada’as.Reb Itzele Peterberger in Pri Yitzchok offers the following answer based on ruling of the Magen Avrohom 308:11. According to the opinion that Shabbos is not the time for Tefillin if one dons Tefillin on Shabbos, he does not have to. The explanation for this is that the obligation is only to avoid diverting his attention away from the Tefillin only at the time the person is fulfilling the mitzvah of Tefillin. However, on Shabbos where he is not fulfilling any mitzvah there is no obligation to because there is no prohibition of hesech hada’as.The Gemara in Eruvin 95 state that if one does not have intention to fulfill the mitzvah of Tefillin he does not fulfill the mitzvah of wearing Tefillin according to the opinion that mitzvos require intention. When a person is sleeping and he is obviously not have any intention in fulfilling the mitzvah at this time he will not be fulfilling any mitzvah even according to the opinion that mitzvos do not require attention. Since he is not fulfilling any mitzvah at the time, there will be no prohibition of hesech hada’as.