You need to determine where the high ping times are coming from. It could be within your LAN, or on the outside circuit.
First thing I would do is test pinging to your own home router. If you see spikes in latency here, the problem is with your home hardware, cabling, or the computer.
If everything looks good in the LAN, I would attempt to reboot your modem. If that has no effect, and this issue doesn't clear up shortly, call your ISP.