Set the DataGrid’s FrozenColumnCount="1".
<DataGrid FrozenColumnCount="1" Name="dgQuestionTemplate" HorizontalAlignment="Left" Grid.Row="1" Width="870" HorizontalScrollBarVisibility="Auto" IsReadOnly="False">
Frozen columns are columns that are always displayed and cannot be
scrolled out of visibility. Frozen columns are always the leftmost
columns in display order. You cannot drag frozen columns into the
group of unfrozen columns or drag unfrozen columns into the group of
frozen columns.
DataGrid.FrozenColumnCount