Then the next step is you have some apps that are bogging down the CPU. There are tools you can use to determine which one. It's not hard just takes a little patience to learn. One way is to disable ALL apps, then use the phone for an hour. If it's Ok, then re-enabled a bunch of them (and write down which ones). If a problem recurs, start disabling those one by one until the problem goes away. Then you know which one is the problem. If the problem recurs, you have an issue with another app... Rinse, repeat...