Finder keeps freezing in Yosemite have to relaunch often

Finder keeps locking up when I click on a single item (vs a folder). If I double click on an item real fast the moment the folder shows its contents, the document or jpg will usually open. I am using OS 10.10.2 (Yosemite) on a Mac Mini. I just installed new RAM - now I have 8 GB - didn't help Finder problem. Color wheel just turns and turns and/or when viewing items in column mode, as soon as I get to a single item, Finder freezes. Exasperating!