I'm a newbie here and I coming with a strange problem (for me...).
Just to introduce my config: I use Blender with an i7 CPU (3930K 6-core), a GeForce GTX660Ti, 32Go RAM, and I work with Windows 10 Pro.
I made often simple scenes, the last one are a dozen of gears which turning and that's all, all frames have the same complexity level.
When I render animation with a render time about 2,5 minutes/frame in 4k resolution for example, as long as I used my computer (to surf on Internet or some little things) the render time is stable, BUT if I leave my computer, after some time, the render time slowing down! And the frame use even 5 minutes!!! If I move the mouse, the next frames becomes normal with 2.5 minutes... Strange, no?
All right, all the time saver are off (screen, hd stop, etc...), please have you any idea about that problem? Thanks a lot in advance!!