How to Disable Burst When Using the Timer
By default, the Camera app will take a series of burst photos when using the timer. There is no way to disable it but there are a couple of alternatives:
1. Enable Live Photo - the iPhone will only take 1 Live Photo instead of 10 burst shots when using the timer together with Live Photo. To enable it, tap the circle icon on the top right-hand corner of the Camera app:
2. Use 3rd party apps like Camera+ 2 - You only get one photo when using the timer feature of this app.