\makeatletter

\def\sect{\@dblarg\@sect}
\def\@sect[#1]#2{%
  \par%
  \nolinenumbers%
  \section[#1]{#2}%
  \linenumbers%
}

\def\subsect{\@dblarg\@subsect}
\def\@subsect[#1]#2{%
  \par%
  \nolinenumbers%
  \subsection[#1]{#2}%
  \linenumbers%
}

\def\subsubsect{\@dblarg\@subsubsect}
\def\@subsubsect[#1]#2{%
  \par%
  \nolinenumbers%
  \subsubsection[#1]{#2}%
  \linenumbers%
}

\makeatother