Q. If one goes to sleep before Shabbos is over and wakes up Sunday morning, must they Baruch Mavdil before doing any melacha?

A. Shulchan Oruch (O.H. 299, 10) rules no to do any melocho until one recites havdolo or says “Boruch hamavdil bein kodesh lechol”. If one forgot or was unable to recite havdolo at the end of Shabbos, there are two dissenting opinions as to if one should recite havdolo during the next three days or only on Sunday (ibid. 5).

Horav Shlomo Miller’s Shlita opinion is that this applies not only to eating but to performing melochos as well.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a