Is it obligatory to say "A'udhu billahi min ash-shaytanir-rajim" (I seek refuge in Allah from the Satan, the rejected) and "Bismillahir rahmanir rahim" (In the name of Allah, the Most Gracious, the Most Merciful) when repeating the recitation of Surat Al-Ikhlas multiple times consecutively?

Seeking refuge (reciting isti'adha) at the start of recitation is a recommended Sunnah. It is not required when repeating a surah unless the recitation is interrupted by turning away or by irrelevant speech, in which case the isti'adha should be renewed. As for the basmala, it should not be omitted when beginning a surah, even when repeating it, because in this case, the surah is considered to be commencing anew.