Can Sundial of the Infinite interrupt multiple-card draws while drawing?
No. 

In order to activate an ability or cast a spell, a player must have priority. During the resolution of spells and abilities, players do not receive priority. 

One advantage of declaring "multiple draws are done one at a time" is multiple card drawing cleanly interacts with cards like Abundance, Alhammarret&#39;s Archive, or cards that say, "whenever you draw a card"