Is there a trigger to buy or sell cryptocurrency when it hits certain prices as like share trading?

Yes, there are triggers. You can use Bittrex exchange.

But you will have to define those ‘certain prices’ of yours. It works exactly the same as stock trading.

You put a buy/sell limit and when the price reaches that certain defined limit, the order get’s executed.

For example, you would like to buy One ETH for 0.01 BTC while ETH is currently traded for 0.15 BTC. So, you put a buy order and when there’s an Ask match, the order would be executed for the same.

Note: Bittrex does not support deposits in dollars/fiat (unless, you are planning to invest $10k). You will have to deposit BTC to trade on Bittrex.

If you would like to deposit with fiat, check out Bitstamp.