It's called "recursion".
The regress argument (also known as the diallelus (Latin < Greek di allelon "through or by means of one another")) is a problem in epistemology and, in general, a problem in any situation where a statement has to be justified.
According to this argument, any proposition requires a justification. However, any justification itself requires support. This means that any proposition whatsoever can be endlessly (infinitely) questioned, like a child who asks "why?" over and over again.