Is it correct to repeat the prayer standing with a single ablution, without paying attention to what comes out, after praying sitting for fear of something coming out?

There are two possibilities for your feeling of drops coming out after urination:

First: What you feel is merely doubt and whisperings [from Satan]. In this case, do not pay attention to the doubt, and do not search for anything coming out. Build upon the original presumption, which is that nothing has come out, until absolute certainty to the contrary is achieved. Do not repeat ablution or prayer, and treat the matter normally. Pray a normal prayer and do not interrupt it due to doubt; for the Prophet (peace and blessings be upon him) said: "He should not leave [the prayer] or turn away until he hears a sound or finds a smell."

Second: What you feel is real and you find its effect in reality, and it is almost always accompanying you. This is treated as incontinence, and the ruling for it is that you perform istinja' after relieving yourself, place something that prevents the spread of what comes out, and perform ablution for each prayer after its time has entered. Pray a normal prayer, and what comes out during the prayer will not harm you.