test the card in another computer  like maybe yiour buddy will in his gaming rig   [ or something not a prebuilt like a hp, or dell ] .  same issue then maybe a bad card ready for rma .
 
when reinstrll of the driver go back to a older driver maybe aroundthe time the 950 was first supported   [lately latest  NVidia drivers can be a crap shoot / just bad ]  I'm still on older like 355.82  /353.62  for my 900 cards .
 
test your memory with memtest .  test the harddrive  [like if a wd drive use there data lifeguard tool for example  ]
 
did you install any monitoring software  ?  [example - I started closing some applications and Corsair Link was the one keeping my GPU clock stuck at maximum. ]
 
for me once asus suite was a big issue on a asus build   and took a lot to purge it out  over just uninstalling it   -never again will that be used  and I don't install crap/gimmickware .   all you need is NVidia drive under custom install and just select the cards driver.  matter of fact I don't even have PhysX installed [not that it does harm  just no need for it  ]    the same with the motherboards stuff   / just the needed driver [if even needed ]  not a drop more    
 
if your using that malware ''service''  called win -10  , well your on your own dealing with what ever Microsoft does to you , sorry  .
 
steam, uplay or origin games ??   well you do agree to things as this for there mandatory clients you got to take first off the bat   that allow you to use there games 
 
 
''you must have a Steam Account and you may be required to be running the Steam client and maintaining a connection to the Internet.
For reasons that include, without limitation, system security, stability, and multiplayer interoperability, Steam may need to automatically update, pre-load, create new versions of or otherwise enhance the Content and Services and accordingly, the system requirements to use the Content and Services may change over time. You consent to such automatic updating''
 
no telling what there doing to you everytime you go online  '' without limitation ''   who in there right mind agrees to something as that willingly ?   not me that's for sure  [opinion]   I don't need to game that bad 
 
 
 
 

ya, when you google that issue around  like gtx 950 freezing  , or stuck at max clockis  ..ect  a lot of posts on it  to look at and see if a fix pops up ?    thing is its everything from a bad card to bad hardware  to bad software  .    weeding it out is where you chase your tail , and hope you luck on to it sooner them way later  on the cause . 
 
testing the card as said above is a good start point if you can then its process of elimination from there ..   also can you borrow a like card from a friend to try in your rig ?

Ugh, I don't have access to another pc right now, there is a normal one but I don't think the card would fit neither if it will provide enough power, its a very old pc :/

Or put in the old video card and see if it works.
 
I would try using MSI Afterburner and set the fans to 100% to see if it still has the issue.
That is what happened to 1 of my cards. It got stuck in pci-e 2.0 mode, and kept throttling. Go to the bios and see if its set to auto, or pci-e gen 2, or gen 3. Unless specified, put the card at gen 3 if possible. Or, if its on gen 3 already, put it down to gen 2. Then to Auto. Then back to gen 3 (this fixed my issue with it getting stuck at gen 2).
Also set nvidia power management (manage 3d settings) settings to whichever is different from what you have now: Optimal power, or Prefer Maximum power (should do this before bios change).
And, last but definitely not least, set msi afterburner to use GPU Temp Target as priority instead of Power Target (just click the little bubble thing, it will move to gpu temp target, then click Apply). This 'should' solve any overheating issues, or throttling issues. You wont have the big OC on it, or even the normal out of the box auto oc, but it should be stable.
 
Also, do you HAVE to have the latest drivers you are on or a game wont play? If not, then go back to a previous known good quality driver (I use 388.00, and can still play farcry5, which is the newest games I have. It warns me about updating, but I can skip it, and it still looks good and everything works).