On top of the recommendations already given, check your wireless router/modem. If it is somewhere that it will get hot easily, it WILL shut itself off as a safety precaution. This goes for those portable ones that have their own battery as well. If you think it is getting hot easily, check to see if there's anything clogging any vents or it being exposed to direct sunlight. If neither seem to be an issue, start it up and wait about 5 minutes after start up to put your hand to it. You can usually feel how warm it is right away.