Is one who unintentionally causes annoyance to his mother and wakes her from her sleep, despite his keenness not to disturb her, considered sinful?

If your actions caused your mother's anger without intent or prior knowledge that she would become angry, then there is no sin upon you, for Allah Almighty says: "And there is no blame upon you for that in which you have erred, but [there is blame for] what your hearts intended. And ever is Allah Forgiving and Merciful." Nevertheless, you should apologize to her and seek her رضا, even if her anger was due to an unintentional act.