What's wrong with this iPod?

Okay, just yesterday my friend texted me saying her iPod was acting up. She stated that every time she tried to open any app it would close on her and would continue to do so through out the day. My being the one who set her iPod up, I went over and restored it for her, then put everything back on it. She owns the iPod generation 4 and never before have I seen this happen. It worked fine after I restored her iPod and all, but just a little while ago she sent me a text saying her iPod was acting up the same way again. It was the same story as last time: she unplugged it from charging and went to open an app. Boom, it closed on her. Could it need an update or what? I don't know what to do for her now. D: