WHY???? Period stops half way through then starts again

I have a pretty average 5-7 day cycle but my period always stops for a day around day three. Ever since my first period I have bled fairly heavy for two/three days then my period stops completely for a day then starts up and finishes for another two days. It’s almost like it drys up for a day mid cycle. I always think it’s over and then it just randomly starts again. I’m assuming this is normal and just how my body works cause it has done this my whole life..... does anyone know why this happens?