lifting spine when turning shoulders

[beachwave]

When I rotate my shoulders, I take the club back on a flat plane and then tilt my spine back away from the ball, then when I start my down swing I lean back down and bring the club down like I am spliting a log. I will try to attach the video so you can see what I am talking about. How can I correct this and have a smoother swing while staying on plane? Beachwave