I'd be in youtube and my phone will close out of youtube in the middle of a video. And I'd constantly have to be clicking back into the app. As I'm typing this my keyboard keeps going down. Sometimes I'll be greeted by ads in the middle of my mobile game, sometimes the game will freeze then start up again. I'd like help finding a way to resolve this issue.
First you need to check the phone for viruses, malware, bad apps, etc. It sounds a lot like something of this nature is interfering with the phone.
Should nothing turn up, then I would suggest you clear out the cache of any of the apps you are having issues with (if a browser is involved clear the history as well) and then restart (turn it off and back on) the phone.
If you recently installed any new apps, or updated any, I would consider uninstalling said app/update, restart, and then see if the problem persists. Sadly apps can install others things.
In regard to the ads, you need to check your apps to see which ones allow for ads (should the above not effect that). Many apps allow for ads. To check if an app allows for them you can go to play store and look at the apps info (in your installed apps list). You can also check which ones on your phone say they do (if listed, the ads option isn't always listed) by going into "Settings" then "Apps". Tap the individual app you wish to check and scroll down. If it does list that it will be there, as well as what permissions that app has.