I know the word cuncti/ae/a means "all", but then I came across the word cunctare or cunctari, alternatively, which means "to hesitate".
Do these two words share a common etymology to some extent?
According to Lewis & Short, cunctus "all" is a contraction of coniunctus "bound together", from con- "together" and iungo "to bind". Iungo is from Proto-Indo-European *(H)iug- "yoke". But De Vaan does not mention this etymology; he only says cunctus may be a contraction of concitus, from con- and cieo "to move, incite". He adds that Ernout & Meillet reject this etymology. Cieo is from Proto-Indo-European *keih2- "begin to move", according to De Vaan.
Cunctor "hesitate" is from Proto-Indo-European *ḱ(e/o)nk-(eie-) "to hang, falter, hesitate", according to De Vaan and Philippa, and it is cognate with English hang.
So the two words are probably not in any way related.