I don't know the exact reason, but whenever I'm watching a video (doesn't matter if it's Youtube or VLC), after some minutes (twenty or so), my CPU usage spikes to 100%. I've been trying to see what is exactly causing it, and the only thing to blame seems to be some processes called kidle_inject:[RANDOM NUMBER]. Now, I've been looking through the internet and it seems it's just some sort of thermal controller for Intel. I'm not sure what's going on out there, but it makes the computer completely unusable. I don't remember experiencing this before. Maybe it's a system update that introduced a bug, I don't know, but is getting really frustrating.
My laptop is a Lenovo T430, with 8 GB of RAM, Intel Core i5 (Haswell, I think), Intel HD Graphics 4000 and a screen resolution of 1600x900.