So I just rebuilt a used computer that I got from a family member. It's running just fine except for one major issue. Whenever I load up an internet browser or do anything at all the CPU jumps to 100% usage and stays there. I could just open Steam or any other program and this happens. If I type anything in the internet browser this happens. It doesn't matter what browser All of the parts are ones that were the originals for this computer. I don't know if this has anything to do with it but when I press the power button it doesn't always turn on the first time. The lights will come on and then it will shut off. I'll press the power button again and it will turn on normally. How could I fix these issues or at least figure out what is causing them? Below are the specs for this computer.
MSI B150M Bazooka Plus Motherboard
Intel(R) Core(TM) i5-6402P CPU @ 2.80GHz (4 CPUs), ~2.8GHz
Corsair Vengeance LPX 16GB
NVIDIA GeForce GTX 1060 3GB
Windows 10 Home 64-Bit
MSI B150M Bazooka Plus Motherboard
Intel(R) Core(TM) i5-6402P CPU @ 2.80GHz (4 CPUs), ~2.8GHz
Corsair Vengeance LPX 16GB
NVIDIA GeForce GTX 1060 3GB
Windows 10 Home 64-Bit