There is no best time to invest I bitcoin for a beginner and jts best to just buy your first portion of bitcoin and after you have matured as an investor then you can start practicing dip buy, most early investors are scared of the volatility of bitcoin so its best they use the DCA strategy that protects them from market volatility since they would be buying at every market price interval, so it's a beginner friendly strategy to start your bitcoin journey.
If someone cannot predict the exact timing of buying then he should focus on the price That if he can afford to buy then think about a percentage which you will invest based on a monthly or weekly basis. I think one should use the method of DCA because there will be no burden on a person to invest in just a single try.
Market volatility should be kept in mind and make a decision according to the volatility so one will not be worried about his loss if he continues investment with patience.