first off, check your battery connections, make sure they're tight and not soiled too bad
next check your alternator, then your starter
after that you may need to have your fuel line looked at
anyone else have any ideas?
ethenol fuel will not vapor lock your car, that is a myth. i used it exclusively when i lived back in iowa and never had a problem with it (they don't have ethenol gas here

) it's true that if it gets very hot (we're talkin 120-130ish) then gas will evaporate, but it's got nothing to do with the ethenol. gasoline just has has a lower vaporization temperature than water. if you live in that kind of heat, then you might look into buying a new gas cap