So many people move their body to turn and ‘look’ to see where their putt has gone way too early! This can create pulls (missing left for a right handed golfer) or a lack of distance control due to poor strikes.
My advice is simple, putt keeping your left side solid specifically your left hip. Set your left leg and hip position at address and work on keeping them 100% solid. I use the word solid as opposed to rigid as I don’t want tension, I just need you to hold the body’s position firmly.
This will stabilise you stroke allowing your upper body to work far more effectively.
So keep control of your hips and legs to hole more putts!