What should you do about the feeling of gas escaping and hearing its sound during the opening takbir (takbirat al-ihram), only for it to disappear when you intend to repeat the prayer, leading to repeated prayers several times?

This is a baseless whisper (waswasah), and this voice is from the deception of Satan to corrupt your worship. Therefore, you must ignore these whispers. Do not rule that anything has exited unless you have certain, firm conviction upon which you can swear an oath.