@ST500 you've not explained what your main activity is doing. Is it loading data from the internet, is it loading images, what task(s) exactly is your main activity setup to do when it is first fired up. It's a waste of time posting with absolutely no explanation about the purpose of your app.
For example I can easily say that an app starts slowly, but if that app is trying to download a 10GB database from an online database server or processing hundreds of images, then that would explain why. You need to explain what the purpose of your app is instead of just saying that you will send the code to Erel when you get home. I'm more than sure that Erel has more important things to worry about.