So, I have a sort of strange problem (I think). I have a fairly new HP ProBook 4520s laptop (its almost a year old) and a few weeks ago it started doing what is said in the title. When the battery is running low and I plug it into the wall, it becomes very slow and shows very high CPU usage (fluctuating, but somewhere about 80-100%). It does this even if I close all programs which were open and just leave it alone. I've tried to use the Task Manager to see if there is anything in particular causing it, but nothing in particular shows a high CPU usage.
The high CPU use goes on for about 20-30 minutes during which time it is pretty much impossible to use the computer, but after this time (I've noticed its usually when the battery reaches about 75% charge) it stops, CPU use drops back down to ~5% and I can continue using the computer. Another way to get around it is to either restart the computer when I plug it in, or wait for it to hibernate when the battery runs out, plug it in, and then switch it on again.
I've done two virus checks (Avast, F-Secure) and they came back clean. No malware as far as I can tell. So I'm not really sure whats going on, only that its rather inconvenient.
If it's relevent, I have had some power issues before, mainly that if I hibernate/shut down the laptop and leave it plugged in, sometimes it restarts itself. Usually I just get around it by unplugging it whenever its off, but maybe the two issues are linked?
I would really appreciate any help!