Can't access internet


I have a problem with accessing the internet. I can get on fine at first but if I go away from the computer for a while and come back the connection is lost. I get the 2 computer icons with an ! at the bottom of the taskbar saying I have little or no connection. I have to restart the computer to be able to get back on the web. I did notice that the IP address changed in Comodo. I have a router and the regular IP address starts with 192.168 and when this problem I just described happens the IP address is 169.254. It goes back to 192.168 after I reboot. Any help would be appreciated.