Tempo is one of the most underrated and least thought of parts of the golf swing. But unlike other swing flaws, it's fairly easy to correct. The traditional way to slow down your swing is the "name tempo." That is the one teaching pros have been teaching for years. It's simple. You just say your name as you swing. First name on the back swing, last name as you follow through. Make sure you say it smoothly and to yourself! It's easy when both are 2 syllables. For instance, "Mich-ael" "Jor-dan" You keep it rhythmic and smooth and swing to the same tempo.
I prefer a slightly differnt technique. When I was a junior my mom was driving me to a tournament when Phil Collins' "In the air of the night" was first out on the radio. As I played that round I swung as smoothly as I had ever swung before in my life. Then I realized I was singing the song in my head before every shot. Find a very even, rhythmic tune and sing it in your head. Try to sing it in your head as you set up for the shot. This also helps you block everything out and avoid "paralysis by analysis" by overthinking. Get a tune in your head and swing to the rhythm.
Try either one on the practice range and see if that helps.