More details please. Is this problem happening only with your home WiFi, or is also an issue elsewhere (i.e. work WiFi, a public WiFi like a local library, etc.)?
If only at home, what kind of WiFi network do you have (a modem/wireless router box or to you have your own router); also do you have other devices (other phones, tablets, laptops, etc) using this same WiFi network and do any of them also drop their WiFi connectivity?
If this is happening both at home and elsewhere, has your S8 received a recent update around the time that corresponds to when this problem began to happen? Or have you installed some network-related app that recently?