IPhone 5s doing things on it's own?

[iMore Question]

I just bought an iPhone 5s from someone and used it for a day and started having problems. It doesn't want to respond from touch some places and letters while typing a message. Then it got worse by not moving at all to my touch and bouncing places on it's own. Opening apps by itself. I called the guy who I bought it from and he said it's the screen that he would replacer he screen for free this week. Could it be just the screen or is it internal?

 

[Rob Phillips]

Welcome to iMore!
How much local storage do you have available in Settings > General > Storage & iCloud Usage? Flinching issues are sometimes attributed to low memory on the device. If you're sitting at less than 1GB available you should delete some things to free up space.
My second suggestion would be to restore it using iTunes and setting it up as a new device in order to weed out a software issue. Use it for a bit before installing any third-party apps to see if the problem replicates itself, the slowly begin adding apps back in. https://support.apple.com/en-us/HT201252