My MacBook hangs, and when I restart it, it quickly gets heated!

Problem: My Macbook Pro ( with Sierra) hangs/freezes when I start an application! I started to notice it when I start my music production program "Studio One". I also noticed this when I start a less "demanding" app like Spotify. And even smaller tool-apps.

When I restart the computer, the fans gets going and the computer struggles with the heat as it's logging into the osx.

Measures: I made the hardware test, but nothing could be found. I checked for virus, nothing particular. I even switched the hard drive and put in one of my old hard drives, and the computer actually hanged it self when installing osx. I doubt that it's something wrong with my ram-memory. I know that my battery been over 2000 cycles tho...

The only thing I can do with my computer is to watch movies, youtube, use Microsoft Word, even Bittorrent and itunes.. yeah.. but not so much more..

My question is: ANYONE who knows what more I can do, and what this might be? I don't feel like anything's "broke" in my computer.. it got to be something minor..