I have same issue on my 2013 Q5 Hybrid. Closing on 127,000 miles now and I started noticing it a year ago. Odd, because it feels like maybe I didn't quite step on the brake properly when hitting "start", but can't be sure that's it. Anyway, it starts 100% on the 2nd try, and has not yet become more frequent or evolved into a larger problem.

At this point I'm not gonna worry about it.