Using an e-cigarette is different from smoking a cigarette. It usually involves taking slower and longer puffs over a longer period of time. This is because e-cigarettes heat a coil in a liquid (think of a kettle). You may find you need to take a few puffs on an e-cigarette at times when you wouldn’t have smoked, but this is nothing to worry about, and the way you use your e-cigarette will develop over time. It’s not like a cigarette, which you smoke from start to finish. With an e-cigarette you can use it once or twice, and then put it away. If you find you’ve got it in your mouth all the time, you might need to use a stronger e-liquid.
If you get a bit of a cough when you use your e-cigarette, this isn’t unusual and it might help to switch from an e-liquid with a high proportion of propylene glycol to one with more vegetable glycol, which can be more soothing.