What does this Wifi trend by iStumbler mean?
From the graph displayed either your router or your MacBook (?) is having problems maintaining a connection. I assume this happens even when the computer is in the same room as the router? This is important as wifi signals are often attenuated by some kinds of building materials (wiring, metal studs, brick/stone walls, longer distances) so being near the router while testing is a good first step.

the fact that thing are OK for a minute or so after resetting your WiFi (power cycling the  router?) may indicate a problem with the router. the trick is what the problem really is.

The second thing I would do is make sure you have the latest firmware on the router. Often times firmware updates will fix connection issues and stability issues with the routers. If it an Apple Airport then the Apple Airport Utility has a button to check for updates.

If it is a non-Apple WiFi router log onto the admin page and record the firmware version. The go to the manufacturers website and see if there is an update and apply it. Even if there is not an update re-applying the current firmware might help. Also you could try resetting to factory defaults.

Failing that you could try a 3rd party firmware like DD-WRT, Tomato or the like, and if those do not work then it may be time to get a new router. A decent router is not expensive, but depending on the construction and layout of your home you might just need more than a base model unit. Just remember that more $$ means generally faster access and better coverage.