I use OmniDiskSweeper (not affiliated). In terminal, run the command:
sudo /Applications/OmniDiskSweeper.app/Contents/MacOS/OmniDiskSweeper
Give it a moment then click through the options and you'll eventually be able to locate the issue. For me, it's typically some cache for an Adobe product thats eating up a monster amount of space.
Hope this works for you!