Brand new WiFi loses internet connection every few hours.

Got brand new internet 3 days ago, and already 4 times I’ve had the modem lose internet connection. Most times it just came back after unplugging it, but this last time it has not. And even if it did, it is unacceptable to have to restart the modem multiple times per day. 

i have made sure it is connected to power, I have made sure the coax cable is attached firmly to the modem, I’ve followed the Xfinity AI’s instructions but the problem keeps happening. 

What is happening?