Can the bedtime Shema be said in bed? I thought I saw a halacha that said that if it is said in bed the person has to say it on their side based on Rambam’s opinion in brachos?
If a person has not yet recited Keriyas Shema at its proper time, one must recite the Shema with all its halachos, and it should not be recited lying down (Mishnah Berurah 239, citing from Magen Avraham).
If one has already recited Keriyas Shema, “Keriyas Shema al Ha-Mita” (the bedtime Shema) can be recited lying down, but this is not the preferred manner, due to the concern that one should fall asleep and fail to recite Ha-Mapil (Shaar Ha-Zion 10).
If one recites the bedtime Shema lying down, one should indeed lay down on one’s side, or at least lean towards the side (loc. cit.).