Answered by Shaykh Faraz Rabbani
During prayer, I see a lot of brothers often burp or scratch themselves. Is this disliked? If one is in-front of Allah (SWT) during prayer, then isn’t that a form of disrespect?
In the Name of Allah, the Beneficent, the Merciful, and all blessings and peace upon our master Muhammad, his Folk, Companions and those who follow their noble way,
If one burps intentionally without excuse and sounds are produced, the prayer is invalidated. If it overcomes one, it is proper to close or cover one’s mouth and prevent a sound, and improper not to do so (though it would not invalidate the prayer).
Any slight unnecessary motion is somewhat disliked. If it becomes akin to fidgeting, it is prohibitively disliked. Though such a prayer would be valid, it would be wajib (necessary) to repent, and to repeat the prayer to lift its deficiency.
And Allah knows best.