If the Timer is already enabled when the Start method is called, the interval is reset. If AutoReset is false, the Start method must be called in order to start the count again.
Resetting the interval affects when the Elapsed event is raised. For example, if you set the interval to 5 seconds and then set the Enabled property to true, the count starts at the time Enabled is set. If you reset the interval to 10 seconds when the count is 3 seconds, the Elapsed event is raised for the first time 13 seconds after the Enabled property was set to true.