MacBook Pro running slow, freezing?
That's definitely a big load but it doesn't sound seem like it's too much for those specs.  It's tough to troubleshoot something like this with a single answer but my guess is that there's an issue with your SSD.

Here's my reasoning:


Temporarily fixed up on Restart.
Temporarily fixed when startup disk is cleaned.
You're running with only 10.7% free space.


Possible solutions:


Verify that TRIM is running for your SDD. It should be if it's a stock drive but if it was updated, it probably isn't running.


In a terminal:

system_profiler SPSerialATADataType | grep 'TRIM'

Looking for "TRIM Support: Yes" but if it's no, the free version of Trim Enabler can do this:  https://cindori.org/trimenabler/

Try running the built-in maintenance scripts.  These should be running on a schedule already but you can manually run them in a terminal.

sudo periodic daily weekly monthly



These do various tasks with a frequency indicated by their name.  You can learn more about what they do here.
 http://thexlab.com/faqs/maintscripts.html#Anchor-The-11481

You might consider upgrading the SSD before investing in a new system.  macsales.com is great for matching up specific hardware id's to appropriate components.  I'm not endorsing that site.  It's just a starting point.


Hope that helps. Good luck.