Add model number, distance to WiFi, WiFi security settings and if your internet protection suite has expired. Some of those antivirus suites close the internet connection after so many minutes "for your protection" but long enough for you to renew.
For a few months now the wifi on my laptop has been going out randomly and the only way to make it come back on is to restart it. It's already happened three times so far this morning and I've finally had enough. I have a Gateway brand laptop with Windows 8.