Having created a number of schedules I am finding that some schedules will run more than once. The schedule will complete successfully and immediately restart itself.

Anyone have any ideas?

Go to Exception Handling.

If your schedule takes ages to complete then CRD will treat it as "failed" after x time. Then it will re-run it y times.

Increase the "Treat as failed" time to about 1.5 times the time it normally takes the schedule to execute successfully.