Latency spikes out of nowhere

Hello all. I would like to start by saying that the issues I'm currently having did not exist roughly 2 months ago. I've been with Xfinity since June of this year. I got the 200 mbps plan and I've loved it. Speeds were excellent for the first 4 months. Since October I've been having random latency spikes. I do quite a bit of online gaming, and have noticed an increasing amount of them. In my games I can see that my latency will spike to an upwards of 300+ or more at times. I've tried rebooting my gateway and verifying my connections are solid. A technician is scheduled to come in a few days, but I wanted to post on here to see if there was anything else I could do myself beforehand. My setup hasn't changed, nor have I moved the actual location of my gateway since I got it. I'm running my computer through ethernet so it being over WiFi isn't the culprit. I've had nothing but a pleasant experience with Xfinity, but it's getting to be unbearable. Any help would be appreciated.