Singing while sitting??

 I'm a newbie here and I've been trying to practice as often as I can. I don't get a lot of time to really practice outside of the time I set aside for the lessons, but I do a LOT of driving. I've been trying to practice while I'm on the road, practicing good posture as best I can. What I'm wondering is, as a beginner with minimal natural ability, is practicing while sitting down advisable? Or could it potentially create bad singing habits? If it is okay to do are there anythings I should pay special attention to?

When practicing seated, sit up with your spine long, your chest comfortably lifted, and your shoulders relaxed. Be careful of the tendency to reach your chin forward or roll your shoulders forward. We want to be just as energized and tall in our seated posture as in our standing!