What is the stock price trend of an IPO? Does it lose steam after a while, or prices will keep increasing?

It depends.

You can have companies which deliver strong performance for shareholders after IPO

or gone downhill after going public

IPO can be riskier than buying equities on the secondary market since these companies may not have a clear path to profitability yet. For short term performance, it depends on the hype and coverage received. For long term performance, it depends on the management team.​​​