I often play without thinking. Each time I do so, I regret it after the game. Playing by rhythm seems to be a habit. There is a flow in a game of go. For example, when you are deciding the course of your game (whether to attack or defend, etc.), you have to spend time analysing. However, once you have decided the course you want to follow, you naturally start playing faster. This creates a rhythm. It is important. However, in talking about making moves without thinking, you are perhaps referring to careless moves. I wonder if during the game you always have your hand in the go bowl and are holding a stone. And perhaps you have a tendency to make your move as soon as the opponent plays his. The first thing is to develop the habit of not taking hold of a stone until you have made up your mind and decided on your move. This in itself will make quite a difference, I think. It is also better manners, so it kills two birds with one stone. Please give it a try.