Number of time server side function called

I experienced a problem today while making a server side function call from browser.

I clicked the button from browser (which calls server side function) only once and I saw that server side function was called 8 times. Iam assuming that connection was lost between the browser and server, so the server side function was called multiple times.

However what is strange is the time difference between the server side function calls. Lets say 1st server side function was called at X hours, then 2nd server side was called at X + 1min, 3rd server side function was called at X + 35 min, fourth was called at X + 45 min. So my question, why so much time difference between server side calls, even though browser button was clicked only once.

Thanks