In my opinion the main reasons for the volatility of Bitcoin are -:

• The decentralized nature of Bitcoin.There is no single authority to regulate it so no one can decide a ceiling and floor for it's price.
• The second reason is the limited supply and the varying demand of Bitcoin.No matter how high the demand is, the supply will be the same which will automatically increase the price.
• The manipulations done by whales according to their convenience is one more reason for the fluctuations in the price.

On the other hand if we talk about Gold then it is a centralized asset ,less volatile, has a clear demand pattern and the supply is also not limited which makes it more stable.