An "up and down" idle fluctuation often points to a vacuum leak. This usually means a poorly seated carburetor, or a cracked inlet boot. That is only if the fluctuation is somewhat rapid and rhythmic. If your idle just fluctuates too much for your liking during operation, you might want to get your carb cleaned, and follow the above directions if your feel your bike is overheating.

Honestly, for a bike as new as yours, I'd be surprised if the inlet boot cracked on its own.