Help, please

I just recently bought an iPod touch. When I use it to either read a book, surf the internet, or use an app about 10 mintues after using it it will start to go hay wire. The "slide to unlock" screen will come on, or the "slide to power off" screen will come up, or the volume will show up, go up to the highest setting and not let me turn it down. I am not sure what is wrong with it?? It worked fine the first week or so, then I put the "best skins ever" on it and it's done this. Did some water get into it??? I followed their directions to a T so I dont' know what could be wrong??? Any ideas?? I have restored it to factory settings hoping that it was just an app that made it go weird.

Any help or ideas would be really appreciated.

Thank you!

Mine was a little flakey when I first bought it - that is, until I did a full factory restore on it. After that, it's been smooth sailing.