Daily rebooting

We stream television through our PS4 and every few minutes we get a buffering error and then it goes back to being fine. It isn't just the PS4 either, it happens on our tablets/cell phones as well. We are always rebooting the modem and it works for about a hour and then we are back to it all over again. We are supposed to be getting the 100 speed, but continuous testing proves that is wrong. Is there anything to be done to stop the buffering, possibly get it to the speed we are supposed to be at? I do not know which Modem we have, (I am at work) I just know it is the combination router/modem.

Also, there used to be a way to send a refresh signal to the modem. Can that still be done?