Mac randomly stopping Internet
Good call on not dumping the kitchen sink. The first step is to run Network  Diagnostics - once when things work so you can see what it does and again when things are broken.

It will guide you through changes to make, so keep a short log of when you run it and what it has green/yellow/red and what changes are needed to fix each breakage.

Over time, you'll probably find a pattern to one thing breaking and can ask a more narrow follow up question.

To run the tool:


Open Finder
Use the Go manu - Go to folder
paste in /System/Library/CoreServices/
Drag Network Diagnostics to your dock so it's easy to access


You can also use the "assist me" button in network settings - it's bottom right next to apply:




https://support.apple.com/kb/PH21585