Cool just noticed you are in Westhaven, I live in Southbury.
Did it work for a long time and suddenly start giving you problems?
you said it doesn't happen all the time, do you stream music, radio or w/e at the same time? Starting with the browser is the right place to start, but since I assume you will be picking up the PC from someone that is working on it. They should know your specs by now. If you describe to them what you do, they can confirm for you if you are taxing your system or not. If you are dealing with a front desk person ask to speak to the tech that worked on the PC if possible.
How old is the computer? WIFI cards can start to act a little flaky after 2-3 years depending on how they are treated or if your system overheats and that is a relatively cheap fix, but depends on what they would charge to install it for you. Simple test if its Wi-Fi plug an Ethernet cable (Cat5e or network cable) into your router and directly to the laptop. turn off Wi-Fi on the laptop and see if it occurs again. With or with out the browser tabs open.