When I look at portfolios, to give a feedback, I often see lots of sketches with too many details. If you decide to draw all details on each sketch you risk losing the “ideation feeling” or that right mood that will bring you to find an interesting proportioned car sketch.
For this reason, I made a car sketch tutorial to explain and show how to just have fun looking for new proportions before thinking about design and details.
In other words, do not close yourself to fast into a styling mood. Proportions come first!