Does the intention to repeat a prayer upon doubting or making a mistake in it – whether before or during the prayer – invalidate the intention, and is my prayer valid in this case, and how do I renew the intention if the prayer is interrupted?

Since the questioner suffers from waswasah (obsessive whispering), she should disregard these whisperings and pay them no mind. Her entering into prayer with the intention of repeating it, or making the repetition contingent upon the occurrence of a nullifier, does not affect the validity of her prayer. If she doubts having omitted a pillar or an obligatory act during the prayer, she should disregard this doubt, continue her prayer, and not repeat it after finishing. As for someone who is not afflicted with waswasah, what they should do if they doubt having omitted a pillar of prayer has already been explained. The scholarly disagreement regarding hesitation in the intention during prayer and the resolve to terminate it has been mentioned, and the opinion that does not invalidate the prayer in this situation is more lenient for those afflicted with waswasah.