I assume that you have a full 12vdc at the battery? I had this issue. Sometimes the starter was fine, sometimes 'click', 'click', 'click'.......then it would start fine on the 4th or 5th try. I found the ring connector on the starter was very loose. I also had the same problem later and thought it was loose, only to find the connector on the positive cable connected to the starter was very heavily corroded.
Try removing the positive terminal and looking at it. replace heavily corroded connectors. Strip back the sheathing and cut back any heavily corroded wire, re-crimp and shrink tube and connect. clean the connections on the starter. Take a look at the negative cable and connector as well.