Most of the time my intentions have been simply implied.
I start with bismillah. It is implied in the making of wudu that I am purifying myself. I guess if I were to take time and reflect on the act of making wudu, I would be able to concentrate on the Salah or the reading of the Quran.
When I hear the adhan, I automatically answer it, unless it is not clear, and then I make the masnoon dua. It is a reflex action now. Does it mean I am doing it without thought or understanding?
Similarly, when I stand up for Salah, I already "know" without thninking what Salah I am going to offer and how many rakaahs. I do not stand and go through in my head that this is that particular time and I have to offer so many rakaahs of Sunnah and so many of Fard. Does that make my Salah invalid?
There are imperfections all right in my Salaah. Of late I keep forgetting how many rakaahs I have offered, but that does not have to do with remembering at the start of the Salaah.
For most of my life I read the Quran silently, without even moving the lips, made the dua silently, without even moving the lips. And my duas have been answered.
I wonder if I have been wrong!