If an instance of circular reasoning is defined objectively then it has no break, and infinite regress is a form of circular reasoning. One might as well ask where a circle begins.
If one wants to know how there is a here & now: a determinate point, this needs to be considered subjectively because the here & now is part of subjectivity, and is finitely bound by birth and death.
The mistake is to try to interpret the subjective here & now in terms of objective ideas (e.g. circles)—ideas created from subjectivity; "reflected light" as Heidegger puts it:
Dasein is inclined to fall back upon its world (the world in which it is) and to interpret itself in terms of that world by its reflected light, … GA 2, H. 21
Thus one can ground a determinate point in an otherwise apparently infinite regress.