Internet help.

Hello, I have had this problem for 3 ish days now and it is rather annoying. I keep on losing connection to my internet. This is how it happens. I'm playing a game I get kicked for no internet, I have Limited access on my computer, I click on my internet bars  right click my internet thingy and click status. Then I click diagnose and everything is better for about 10 minutes, then it says that my default gateway is closed or something and that is what it diagnoses. How do I permanently fix this problem and what is wrong with my internet? Then sometimes my modem just restarts itself automatically. Help!