Problems with Latency

I’m having intermittent latency spikes and packet loss while gaming on a wired Ethernet connection. My ping to the local Xfinity gateway at 10.0.0.1 stays consistently around 0–3 ms, but the first reachable Comcast hop and external destinations intermittently spike above 100–250 ms, with occasional packet loss/timeouts.  
I checked the XB7 signal levels: downstream power is roughly +1 to +3.5 dBmV, downstream SNR is mostly 42–43 dB, upstream power is about 47–49 dBmV, and there are no uncorrectable codewords or recent T3/T4/ranging errors.  
Can you check the connection from the gateway upstream, including node/CMTS congestion, upstream noise/ingress, and whether there are intermittent signal or latency issues in the area?