I started out vaping occasionally months ago, so I can relate. I was even a non-smoking ex-smoker at the time, hadn't touched a cigarette in years. I had some symptoms even on low-nicotine e-juice. I eventually adjusted to the level of vaping, though.
Blu's at 16mg made me a little sick feeling, and I wasn't even chain vaping. However, I have a lot of experience with nicotine in the past, and OD (I did snus, dip and so on, too, and I think that helped me know my limits), so I knew how to handle mild nicotine overdose and to be cautious. I think a lot of smokers don't have this quite as often. Well, vaping is a lot more like snuff, snus, or dip than smoking. The nicotine is absorbed a lot more slowly and the overdose wears off a lot more slowly. So you can't vape like you are hot-boxing a cigarette, you can vape yourself sick doing that.