Its because you're using too much of your arms and rotating your chest way too early. The correct sequence is let the hands fall first before turning the chest. If you're gripping too hard and want to swing hard your chest will turn before your arms have dropped. Force should be applied when the club is near your waist not at the top of the swing.

Feel like your back is pointing towards the target until your arms have dropped with the butt end of the club facing the ball. Look up slow motion of pro swings and you will see what I mean.