Nobody knows exactly when is the perfect time, the only advice you'll need is that the best time to have bought bitcoin was 10 years ago and the next best time would be now, this very movement. Buying bitcoin and hold is the best form of investing in the industry, as an investor you should buy and wait and not wait to buy as you could probably miss the chance of buying lower than this current price in the next months to come.
You can buy in fractions (batches) if you're not that convince of the price not falling than what it currently is. You can first go in with $100 and wait for the reaction of the market. The industry as a whole is bullish and don't think the bear would be coming anytime soon, you better act fast.