What is the best solution for the problem of obsessive doubt (waswas) regarding intention at the beginning of ablution (wudu') and prayer (salat), which leads to extreme difficulty in commencing acts of worship?

The matter of intention (niyyah) is easy. Whoever stands to perform ablution or prayer has already made the intention. Abandoning it is what is difficult. If Allah had burdened us with an act without intention, it would have been an unbearable imposition. As for saying Bismillah (tasmiyah) before ablution, scholars have differed on whether it is a condition for the validity of ablution. The majority of them hold that it is a Sunnah (recommended act) and not obligatory. Do not resort to swearing an oath at the beginning of an act of worship, as this is due to the influence of waswasah (whispers/obsessive thoughts). The cure for waswasah is to completely disregard it, pay no attention to it, proceed with the act of worship, seek refuge with Allah from Satan, and frequently supplicate to Allah.