I have to create a table with math symbols in the header and numbers in the body. I would like to align all the numbers to the decimal dot. To do that I used the siunitx package. The problem is that I am getting a "missing $ inserted" error because of the header, although all the $ are at the right place. Can anyone help me?

Here is a MWE:

```
\documentclass{article}
\usepackage{booktabs}
\usepackage{siunitx}
\begin{document}
\begin{table}
    \centering
    \begin{tabular}{*7S[table-format=-3.2]}
        \toprule
        $\varphi$ & a & $\xi$ & $\alpha$ & $\beta$  & $\dot{W}^{M1}$ & $\dot{W}^{M2}$  \\
        \midrule
        0.00 &  45.00 & 22.48 & 0.02 &  0.17 &  250.00 &    250.00  \\
        1.00 &  45.50 & 52.21 & 44.82 & 38.39 & 236.86 &    236.72  \\
        \bottomrule
    \end{tabular}
\end{table}
\end{document}

```

Thank you