Shuffle button question/frustration

OK, let me say first that I really like my iphone 4 and all of the options I have now. With that being said when I play a song in music, somehow the shuffle button gets pressed (sometimes I swear I don't even press it and it still shuffles) when I don't even press it. It shuffles after a few measures of a song to the next song and it gets really annoying. I went to the Verizon store and the rep there just gave me the "ohh shucks" speech and did nothing.

Why does this happen? Is there some sort of forceful presence or way that I'm holding the phone from the outside that enables this shuffle option? Its just getting really frustrating when I play music and this happens.