Android takes more time on application start up during first time launch

There is an issue in version 2.0 and 2.1 of android studio, but the answer is simple. You must go to Preferences/Build, Execution, Deployment/Instant Run.

Then when you click on "Instant Run" in the right side will appear 4 options with a checkbox for echa one, you must uncheck the first and the last one. Finally click Apply,Ok. And that's all.

That will solve the problem

There is a strange issue with newly released Android Studio 2.0 or 2.1. First time of launching application take longer than usual. This issue happens only in debug mode and not effect to your released APK. Also I was suffering this issue and found this solution.

Settings/Preferences(Mac) → Build, Execution, Deployment → Instant Run and uncheck Instant Run

This will solve your problem and if it is please mark as accepted answer.