Why does my text insert on the same line as my section title?

Question

I want to use section numbers with the following sequence:

1 Section

1.1 Sub Section

1.1.1 Sub Sub Section

1.1.1.1 Sub Sub Sub Section

I have found a way to do this using the following code but when I am getting to the 1.1.1.1 level the text is following on from the title rather than below it. I'm guessing it is to do with the fact i use \paragraph to get the section numbering I want but I don't know how to fix it.

I have tried adding various \vspace commands in but nothing I have tried has worked so far.

\documentclass{article}
\usepackage[utf8]{inputenc}

\setcounter{secnumdepth}{5} %allows for sections 1.x where x = {x}
\begin{document}
\section{Section}
Some text.
\subsection{Sub Section}
Some text.
\subsubsection{Sub Sub Section}
Some text.
\paragraph{Sub Sub Sub Section}
Some text.

\end{document}