Computer locked, leave it alone, graphics card fans start going.

[0nion1999]

So i locked my computer (Windows key + L), and i left it alone for a while (5-10 minutes) then the graphics card- Asus Strix GTX970 DC2OC - fans kicked in for no apparent reason and would stop as soon as there was any input from me. The fans only turn on when the card needs to be cooled down and it hadn't been used for at least an hour and the case temperature was cool.
Now, i highly doubt it would be this but i heard of a thing that would use your computer for bitcoin mining whilst you were not using it and stop as soon as you returned to stop you knowing about it. This is the first time i have noticed it and didn't find anything online so i am a little worried, but im sure it's nothing. Thanks for any feedback.

 

[hang-the-9]

Has this only happened once or happens every time? Did you do a virus scan on the system? Use a couple of programs, AVG free is good and Malwarebytes.

 

[0nion1999]

Has this only happened once or happens every time? Did you do a virus scan on the system? Use a couple of programs, AVG free is good and Malwarebytes.

I only noticed it the other night. i woke up the computer and the fans stopped, then locked it again and waited and it started again. I tried to get it to do it again today but i couldn't, and everything i could think of was the same. I did run an Avast scan, but i will run a malwarebytes scan soon.