Red x over internet connection at random times?

I've been having a strange internet issue at my apartment for college. Sometimes I will be browsing the Internet at the other end of the apartment when I'll randomly get a red X over the Internet connection icon on the taskbar, even though the Wi-Fi on my laptop is on. Even after flipping the switch and looking through the Network and Sharing Center, I cannot resolve the red X and have to restart the system. Once I do, I get my internet back. Sometimes, it doesn't happen at all. Other times, like yesterday, it happens throughout the entire day every thirty minutes or so. It seems to vary with how well my cable is coming through. (We get both internet and cable through Comcast).

I've observed this issue mainly in my bedroom, which is on the second floor at the opposite end of the apartment, probably the furthest point away from the router and modem. Usually, it works fine when I go into the living room near the router and modem. However, I had it happen there today as well.

I have never had this issue back at home, no matter where I am in the house. I did have it happen at a condo we rented for vacation, but it only happened in one room. Otherwise, I've never observed this issue anywhere else that I've used this laptop.

So, I am curious if you have any suggestions as to what could be going on. It seems like it could be a router/modem issue, but I'm not sure.