(serious prob)being blank for few mins and again becomin normal?

a frnd of mine have this prob...may be some brain prob..he goes blank for few mins..he wt be able to speak nor listen...he jus makes a sound and stares...nd after few nibs he satrs sweating badly nd becomes normal..nd he wnt knw that he went through that...ppl plz suggest me wt to do and y is dis prob..plz help