Dlink wireless WBR 2310 router not working?

I have an arris modem from cox cable in Arizona and a dlink wbr 2310 router. From time to time the router will reset and load up again, in about 20-30 seconds, but just recently I've had to go and unplug the router for a good 15 minutes and plug it back in and hope it works.(this started last night, and I left it how it is currently for about 30 mins and it worked perfectly fine again.) Currently I've plugged and unplugged it multiple times and it still hasn't worked, even though I was connected maybe an hour and a half ago and it worked fine. Currently we have 2 computers, a phone, a tablet and an Xbox connected to the Wi-Fi but it isn't working on any of them (by the way I'm using data right now on my iphone.) it was working fine and then it just stopped. There's two lights, one with 3 circles and the other a Wi-Fi symbol and the 3 lights are lit up along with the four "computers" on the other side, but the Wi-Fi symbol isn't on. I tried resetting the router but not the modem and nothing happened, and when I unplug everything except power on the router the same lights show up. It might be defective but I don't know why it's only defective now.

I'm not totally familiar with this router, but to me it seems like you might have a problem with overheating of the unit. Look on it for the vents on both sides of the router and make sure that one set of vents is on the bottom and the other is on the top. You might also get a fan to blow through the unit. You could also get a can of compressed air and blow out any dust that may be causing a problem with the unit. The ambient temperature of the room may be an issue as well.