I'm quite new myself, it's now been about a month and a half of bike commuting for me after 20 years of not being on a bike at all. My commute is much shorter than yours, though, so no issues with backpack and saddle discomfort (the latter happened on the first few rides, but then disappeared, just like everyone said it would).

I stop properly, but I do a semi-proper start. About half of the time, I manage without the shuffle; the rest, even though the right pedal is in the correct position, I still end up doing the shuffle in addition. I'm working on it. I can vouch it's not the best technique - it looks silly, but it also proved somewhat dangerous to me once, as I managed to catch the toes of my left foot inside the tram tracks mid-shuffle. That particular thing I'll never do again, as I almost fell (no tram approaching).

In my case, I think the shuffle is psychological; I'm not quite 5'2", and while my bike fits correctly, it's a real grownup bike! Wow, I'm riding an adult bike for the first time in my life, I have it in my head I need some propulsion to get up on that horse's saddle.