Is the missing of my Asr and Maghrib prayers, after feeling tired and sleeping with the intention of waking up to perform them, caused by a sin, while being keen on performing all prayers and supererogatory prayers?

Not waking up for a supererogatory (nafila) prayer does not necessarily indicate a sin. It is permissible to sleep before the prayer time enters. What is recommended is to take measures to ensure waking up. However, after the prayer time has entered, it is not permissible to sleep unless one is certain they will wake up before the prayer time expires, or they have appointed someone to wake them. It is obligatory for anyone who misses prayers due to sleep to pray them upon waking up. By doing so, they are not negligent or sinful, for the Prophet, peace and blessings be upon him, said: "There is no negligence in sleep."