The momentum effect is that if the bitcoin price rises continuously over a week, it may keep growing for the next week. This is a common feature of almost all known asset classes, and we have found that the momentum effect strongly affects the cryptocurrency. We have designed a simple investment strategy in which investors buy Bitcoin only when their price increases by more than 20% from the previous week. This strategy has excellent returns and a very high Sharpe ratio. 
Actually people will always uses their chances to sell their bitcoin when it's price rise even if only 5% of price increasing. Recently we know that bitcoin price is not move up more than $7000, it's happen because the less of big investors who invest their money in bitcoin. You are talking about positive condition of market but this will happen only if there is a good sentiments for bitcoin price such good news that spread or the improvement of technology which can support the bitcoin usage by people.