My best educated (?) guess is to use the "back" button instead of the home button.
Using the "home" button still leaves the apps running in the background instead of exiting the app. So you constantly have apps running in the background.

 

This may help as well:

https://play.google.com/store/apps/details?id=com.jrummy.cache.cleaner&hl=en&referrer=utm_source%3Dgoogle%26utm_medium%3Dorganic%26utm_term%3Dcache+cleaner+by+jrummy

 

If you are using task killers, stop doing that.

 

With the phone on pull the battery and then sim card. Let set for about a minute. Put sim card and battery back and power up. It should be a bit quicker.