What can cause this?

[JonesY]

Mine doesn't DC but pages stop loading for a couple of minutes or videos stop buffering, quite similar to Grantduke's problem.

Which lights change (stop emitting light, change colour etc) on your modem when the issue occurs? Tried a different internet browser? Tested it with an Ethernet connection instead of wifi?

 

[JonesY]

the neighbor over the road has exactly the same problem. And then my internet disconnects, his internet also disconnects

Using wireless or an Ethernet connection?