Convert a Tif raster file to vector shp file in QGIS

So I've been trying to convert a georeferenced Tif raster file into a vector shp file using QGIS. It's seems to complete this but it ends up giving me a feature class that has over 500,000 features, almost like it's creating a row per pixel. So with that many features it's very hard to work with and when I do finally get it to Classify like into 8 classes of natural breaks, it doesn't look like the original tif file. My end goal is to only have a few (less than 20) polygons based off the raster not thousands. Could it be that the Tif file I'm using is already pre-processed or something?