  Anomalous Microwave Emission (AME) is an important emission component between
10 and 60 GHz that is not yet fully understood. It seems to be ubiquituous in
our Galaxy and is observed at a broad range of angular scales. Here we use the
new QUIJOTE-MFI wide survey data at 11, 13, 17 and 19 GHz to constrain the AME
in the Galactic plane ($|b|<10^\circ$) on degree scales. We built the spectral
energy distribution between 0.408 and 3000 GHz for each of the 5309 0.9$^\circ$
pixels in the Galactic plane, and fitted a parametric model by considering five
emission components: synchrotron, free-free, AME, thermal dust and CMB
anisotropies. We show that not including QUIJOTE-MFI data points leads to the
underestimation (up to 50 %) of the AME signal in favour of free-free emission.
The parameters describing these components are then intercompared, looking for
relations that help to understand AME physical processes. We find median values
for the AME width, $W_{\rm AME}$, and for its peak frequency, $\nu_{\rm AME}$,
respectively of $0.560^{+0.059}_{-0.050}$ and $20.7^{+2.0}_{-1.9}$ GHz,
slightly in tension with current theoretical models. We find spatial variations
throughout the Galactic plane for $\nu_{\rm AME}$, but only with reduced
statistical significance. We report correlations of AME parameters with certain
ISM properties, such as that between the AME emissivity (which shows variations
with the Galactic longitude) and the interstellar radiation field, and that
between the AME peak frequency and dust temperature. Finally, we discuss the
implications of our results on the possible molecules responsible for AME.
