The break down:

Car:1998 Civic Ex 5sp

Problem: Cluster - When driving, the speedo will work fine for about 3-4 minutes. Then out of nowhere, or sometimes when I hit a bump, it will start bouncing up and down then sit at 20mph. Every once in a while it will start to work again like normal. Sometimes when I sit at idle it'll do the same thing. Starts bouncing and then sits at 20mph. Then when I start driving it, it'll work .... sometimes.

Could it be the cluster itself or could it be the speed sensor? Or what other issues could it be?