Is it obligatory to set a phone alarm for Maghrib prayer if sleep overwhelms one after Asr, knowing that sleeping after Asr leads to missing the prayer time, and that fragmented sleep harms general health?

One who is sleeping should take measures to wake up for prayer, such as setting an alarm or appointing someone to wake him. This is recommended, not obligatory, because prayer is not obligatory until its time has entered. A person is not addressed by it before the time enters. Therefore, he does not sin by sleeping before the time enters, even if he is certain he will not wake up.

As for sleeping after the time has entered, if he thinks or knows that he will sleep through the entire time, it is not permissible unless he appoints someone he trusts to wake him.

Some contemporary scholars have indicated the obligation of setting an alarm or appointing someone to wake him. The questioner, who mentioned his situation, should be directed to try not to sleep at a time that interferes with prayer. If he needs to sleep at other times, there is no harm in it, and he is not required to take measures.