That’s only how we humans perceive it because we exist in time. Naturally, when God “reaches” into time, it appears to us as movement because of the limited nature of our continuum. But even what we perceive as God doing is in fact part of his unchanging nature. What he does to us in time is in fact “part” of his eternal Act.
But God by himself cannot move; it is impossible. Otherwise, if he were capable of movement, that would mean in one moment, he would be in one place but not in other, then the next moment, in another place but not in the previous. This would therefore mean a finite God, which is contrary to the faith.
Or even if we were to limit “movement” to “doing”. Still not acceptable because this would mean God is doing something at one time but the next he is not doing it anymore. This means he’s (1) bounded by time and (2) finite, since he is doing something then ceasing to do it. This means there is cessation in God and something in him (operation) is not infinite. For an infinite, eternal God, this is not possible. This is what we mean by “God is pure Act”.
Since in God there is no past, present or future, only “now”, there is therefore no movement in him, either spatially or operationally. Anything he is and does are infinite and eternal.
Actually, there is no “now” in God either. There is only “is” in God. We are only “now”, always in our being “now”. We are not in our past nor in our future, we are only materially “now”.
Moses went up the mountain to talk with God, and when he came down he told the people a prophet, not unlike himself, would be coming, “Listen to him.”
But while he was on the mountain, he was joined by five others, Elijah who had climbed the mountain, and by Jesus, James, John, and Peter. Jesus appearance was shining with the appearance of who he really is. As he was going down the mountain, Moses overheard the enjoinder by Jesus’ Father “Listen to Him, my beloved Son”, and so he told the Israelites about the one coming, that they should listen to him.
In the knowing of God, all are, all is, known, simply. And these six were all in the knowing and seeing of God in that “time” on the mountain.
Some perfection, fullness, of being, is “rest”, non-movement, such as when a rock dropped to the ground reaches its terminus and comes to rest of non-movement. Other things are complete, at their final end, their perfection, their ACT, when they operate perfectly, and that is God, operating perfectly in knowing, generating, spirating - all the movement of relationship of Father, Son, and Holy Spirit, and in his perfection of knowing, all that is known “is”, has being, whether eternal (as the Son), or contingent and non-eternal.
Every moment of Moses IS for God, always known. But Moses only apprehends “moment after moment” of what God knows in one knowing.