How does one bring to mind the intention of performance and obligation, and what is meant by the necessity of the intention a short time before worship, and what should be done during that time?

Intention (niyyah) is purpose. Whoever intends to do something has made the intention for it. It does not require elaborate effort to bring it to mind.

So, if the time for Fajr prayer enters and one stands up intending to pray it, the intention for the obligatory prayer and its performance has been fulfilled. Jurists do not stipulate the intention of whether it is an ada' (on-time performance) or a qada' (make-up) prayer.

As for the meaning of intention shortly before an act of worship, it means intending to perform it a short time before commencing it, according to common understanding.

Excessive scrutiny in this matter may lead one to waswasah (obsessive whispering). We advise the questioner, whose previous questions indicate that they are affected by waswasah, to fear Allah and not to give in to it. Let them know that if they stand for prayer intending to perform it, the intention for the prayer and its performance has been fulfilled, and that is sufficient.