Then it is the pretty standard troubleshooting run a tracert and maybe it by itself will show the problem. Otherwise you ping the first couple of hops in the trace and try to see where the increase is. If the problem is in the first hop it is a issue with your router or pc. If it is ok in the first but starts in the second you have a issue with the wires coming to your house and you need to call the ISP.
Things past the second hop represent problems in the provider network. There is little you can do about this, you have to hope the ISP knows about the problem and is trying to fix it. Sometime it is a problem in a ISP that is not yours so they can not do anything anyway. Many time this is caused by some failure in the network like a cut fiber and you are on a backup connection.
To be able to fix it you have to hope it is in the first couple hops.