How will you know when to buy and how will you know when to sell?
Whoever knows the answer to this question will become the most successful trader.
Even though there is no real bad time to buy Bitcoin if you intend to HODL for the long term
of indefinitely but for trading you could very well buy and sell later at the most inopportune time.
If so, can a trader gradually transform into a long-term holder?

You are right that the market volatility offers good opportunities to trade but that comes with risks
for the newbies . . . and there is no easy trades, you will have to put the time and study in.
Trading is fraught with risk, not only for beginners but also for experienced traders. Risks are always present.
No matter how much time and research you spend, there's always the possibility that the president of some oil-rich country will be kidnapped by another country, causing a sharp spike in demand for bitcoin. What trader could have predicted this event, given that a week or two ago, the market was falling and forecasts were pessimistic due to the (presumably) completion of the bull run?
Of course, such price surges offer great trading opportunities, but if you "make the wrong bet", failure is inevitable. Would a newbie want to continue trading after such a scenario? Unlikely.