First line after new section or subsection is indented left

Question

I'm brand new to latex and I'm using it to type up my physics homework, so it's almost all equations. I'm using a section for each problem and a subsection for each subproblem.

The first line when I open a new section, is indented more to the left than the following lines. I would prefer all the lines to be indented at the same level. Any advice?

Here is how I do the beginning of a new problem:

\section*{Problem 4}

Let $\vec{a}$, $\vec{b}$ and $\vec{c}$ be vectors corresponding to the three sides of a triangle.
Let $A$, $B$ and $C$ be the angles opposed those sides.

Here is my header:

\documentclass[16p, oneside]{article}
\usepackage[utf8]{inputenc}

\newcommand{\uvec}[1]{\boldsymbol{\hat{\textbf{#1}}}}

\begin{document}