Why is my ping fluctuating from <50 up to 600 ms? I'm not downloading anything, am located in Poland.
Sounds like a personal issue, as i'm from australia and i get VERY bad ping, but its not inconsistent like yours mine stays at 350-370ms.
I would contact your ISP and find out whats happening.
You can also try a program called "Netlimiter" to see if any programs are downloading in the background.
Could also be someone on wifi making you lag spike.
Was just my modem.