Remove header/footer from titlepage BEAMER

Question

I use Beamer for my presentation. I am using the Berlin theme. I would like that only the title page (first slide) did not show the header and the footer line indicating the index of the topics, the title, etc. I tried to use [plain] just after \begin {frame} of the first slide but it takes away the university logo (I don't want to take it off). How can I solve? Thank you

I would like to add the University logo in the same position of all other frames (Berlin theme).

\documentclass[12pt]{beamer}
\usepackage[italian]{babel}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}

\newcommand{\pngfigspath}{./figures_png_beamer/}

\title{Indagine numerica sulle prestazioni di una turbina eolica ad asse verticale di tipo troposchiano}
\author[UniBG]{\texorpdfstring{\large Alessandro xxx\\ \small Relatore: Chiar.mo xxx\\ \small Correlatore: xxx}{Alessandro xxx}}
\date{Tesi di Laurea Magistrale, xxx}
\logo{\includegraphics[width=20mm]{\pngfigspath Uni}}
\institute[Uni]{Corso di Laurea Magistrale in Ingegneria meccanica\\Università xxx}

\usetheme{Berlin}

\begin{document}

\begin{frame}%[plain]
    \maketitle
\end{frame}

\end{document}

Answer 1

You have to temporarily deactivate the headline and footline templates for the titlepage and then reinstate the ones from the Berlin theme afterwards. The command to set a specific template is \setbeamertemplate and you already found out that headline/footline are the corresponding ones you need to change.

To clear them, just call \setbeamertemplate{headline}{} and to reinstate them call \setbeamertemplate{headline}[miniframes theme], be aware to use the right brackets!

Here is how to use it in an extended MWE of yours:

\documentclass[12pt]{beamer}
\usepackage[italian]{babel}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}

\title{Indagine numerica sulle prestazioni di una turbina eolica ad asse verticale di tipo troposchiano}
\author[UniBG]{\texorpdfstring{\large Alessandro xxx\\ \small Relatore: Chiar.mo xxx\\ \small Correlatore: xxx}{Alessandro xxx}}
\date{Tesi di Laurea Magistrale, xxx}
\logo{\includegraphics[width=20mm]{example-grid-100x100bp}}
\institute[Uni]{Corso di Laurea Magistrale in Ingegneria meccanica\\Università xxx}

\usetheme{Berlin}

\begin{document}

\setbeamertemplate{headline}{}
\setbeamertemplate{footline}{}

\begin{frame}%[plain]
    \maketitle
\end{frame}


\setbeamertemplate{headline}[miniframes theme]
\setbeamertemplate{footline}[miniframes theme]

\section{Section}
\subsection{Subsection}
\frame{A frame}
\frame{Another frame}

\end{document}

And this is the title page and first slide:

Answer 2

Similar to the answer by @TobiBS, but to make this theme independent, one could redefine the head- and footline templates within a group, so this affect the other frames:

\documentclass[12pt]{beamer}
\usepackage[italian]{babel}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}

\title{Indagine numerica sulle prestazioni di una turbina eolica ad asse verticale di tipo troposchiano}
\author[UniBG]{\texorpdfstring{\large Alessandro xxx\\ \small Relatore: Chiar.mo xxx\\ \small Correlatore: xxx}{Alessandro xxx}}
\date{Tesi di Laurea Magistrale, xxx}
\logo{\includegraphics[width=20mm]{example-image-duck}}
\institute[Uni]{Corso di Laurea Magistrale in Ingegneria meccanica\\Università xxx}

\usetheme{Berlin}

\begin{document}

{
\setbeamertemplate{headline}{}
\setbeamertemplate{footline}{}
\begin{frame}%[plain]
    \maketitle
\end{frame}
}

\begin{frame}
content...
\end{frame}

\end{document}