This is my 2 cents worth. I have no specific experience for Samsung SSDs but I do have a fair amount of experience with Mac Laptops and MacMinis with SSDs.
I am post specifically because I have been fighting with an apparently "similar issue" and have come to the conclusion that SSDs are more tricky than hard drives fro a troubleshooting point of view. I have had to return a few SSDs to the manufacturer ( distributors ). In fact, I returned one to OWC just today that has resisted attempts to update it's firmware - twice over several months and began exhibiting poor performance and I was having kernal crashes that I believe were SSD related. I use a utility called "Trim Enabler" for two reasons: 1) I like to watch metrics that perhaps give insight on storage health - the observable health parameters of the SSD and a second Harddisk on my 2012 MacBook Pro and 2) because it turns on the Trim functionality which SOME SSDs like ( need ) or something....
While OWC ( macsales.com ) is a Mac specialty supplier and appear to be experts and have been good to me over the years, but in this case of SSDs, they have failed to come up with a way that I have access to test my own SSDs or a surefire efficient way to identity if the SSD is the issue or if firmware update will help and thus I returned the SSD today and replaced it with a Crucial SSD which uses different firmware - Sandforce firmware. I have experience with the Crucial SSDs for almost 4 years on Mac's and they seem to work well. It was Crucial who told me to used the 3rd party software called Trim Enabler to "enable trim" after I experienced significant performance issues that Crucial tech support believed was because the SSD was not doing necessary maintenance on itself - i.e. Trim.
Now with all that said, I believe there is still a bit of black magic going on - perhaps it is just marketing and/or marketing secrecy so that SSD makers secret sauce does leak out. Personally, I don't like the effects of the secret sauce on the end user's ability to get genuine information and tech support so they can make informed decision on their purchases of SSD.
Even so, I might recommend you try a OWC or Crucial SSDs based on those companies recommendations and warrenty policies. I no long expect trouble free saling or perfect performance or zero maintenance for a busy SSD. I have never done firmware updates on hard disks but SSDs appear to need these firmware tweeks.
I would love some genuine information at the global statistics level, so that I can better gauge my experience against what the global pool experience is showing.
Don't get a 128GB SSD. You don't want to run a 3rd party SSD on OS X without a decent amount of free space since you won't have TRIM support.
Does Activity Monitor show memory pressure? If not, I'd save my pennies until I could afford a 256GB or 512GB SSD. I've done both RAM and SSD upgrades many times and an SSD has always been by far the best upgrade in changing the "feel" of the computer.
Best Answer
Without seeing your Activity Monitor, it's tough to say what your CPU is doing. However, a 24 degree temp swing in a couple of seconds is a lot.
Have you tried AHT (Apple Hardware Test)?
https://support.apple.com/en-us/HT201257
My thinking is that you may have a bad temperature sensor (or it's getting bad info).
If that's the case, there are folks who repair things like this, or it just may be a good reason to upgrade your Mac. There is a guy in NY that does really good work (I am not affiliated) repairing these boards: https://mailin.repair/