Don't know why it happens, but various routers I've had have done this from time to time (including my current one from Sky) and it seems to get worse over time. Once it starts to happen regularly I've just bought a new one (or have changed broadband provider and got another free one). I think its a symptom of them getting old. I wonder about some component overheating or something... Perhaps give it a go with an air blower or something (careful with hoovers due to static electricity and high power settings).
Many of the routers on the market have the same chips inside them so they are all much of a muchness as far as reliability is concerned. In my opinion, unless you have an odd network setup, they are all pretty easy to configure.
Some have a button on them allowing a quick setup (standard is "WPS" but it can also be branded as "Push to Connect" or such like). If all your devices support it (most new devices do) then it makes setup pretty much plug and play.