I have the same problem sometimes. For me it usually is attributed to trying to score instead of just letting go. For instance I was playing in the club championship qualifier and was extremely nervous. Needless to say I shot a 45 on the front 9. Upon making the turn my caddy goes to me, "alright lets shoot even on this side". On the 10th hole I hit my 3rd shot into the par 5 to 2 inches. I eventually stopped trying to control everything and shot 35 on the back nine with a double bogey, a bogey and 3 birdies