high latency at gateway

I started noticing really high latency about two weeks after the installation of a new comcast modem.  I tried disconnecting the coaxial cable from the modem and reconnecting it and the results were spectacular!  I went from latencies upwards of 500 ms and download speeds of 50 mbps (not bad but the latency was really killing me) to normal two digit latencies and download speeds exceeding 500 mbps.  It was really hard to unscrew the coaxial cable - tightness was not the issue then.  Now (no more than a month later) I'm having the same issue again.  I tried using a wrench to tighten up the connector a little bit but it didn't help.  Disconnecting and reconnecting the coaxial cable once a month is not a solution, so I'm not even going to try that again.  Here's a traceroute:

tracert 8.8.8.8

Tracing route to dns.google [8.8.8.8]
over a maximum of 30 hops:

  1    <1 ms    <1 ms    <1 ms  192.168.1.99
  2   983 ms   712 ms  1119 ms  96.120.66.193
  3   556 ms   126 ms    72 ms  68.87.153.177
  4   855 ms   344 ms   223 ms  be-334-ar01.needham.ma.boston.comcast.net [96.108.70.141]
  5   433 ms   718 ms   756 ms  be-32011-cs01.newyork.ny.ibone.comcast.net [96.110.42.1]
  6   773 ms  1130 ms   112 ms  be-3112-pe12.111eighthave.ny.ibone.comcast.net [96.110.34.34]
  7  1070 ms   330 ms  1231 ms  66.208.229.82
  8   870 ms   495 ms    95 ms  74.125.251.231
  9   192 ms   265 ms   536 ms  172.253.72.129
 10   507 ms   424 ms  1330 ms  dns.google [8.8.8.8]

Trace complete.

192.168.1.99 is my firewall (aka "security edge") and the modem is in advanced bridge mode, which is why it doesn't show up on the trace.  When I ping the modem (10.1.10.1) I get a response time of 1 or 2 ms.  For that reason I'm convinced that the problem is not with any of my equipment.  What can I do?