Why do I do it?

I dont know if there is something wrong with me or if it’s quite common, but sometimes I feel like not eating. Like at all. And if I do it, it lasts for a few days - like a mini fast. Then I eat again. Then a couple of weeks later the same thing happens all over again :/ I know it isnt healthy to do it, but sometimes it just comes … naturally? if you like. Is this common, or what is it? Thanks x x :)