Trading is when you buy a altcoin for a low price and sell it when its price comes up so you will have to keep an eye on the market.
Risks? The most common risk is the altcoins short life span, If you search in google, you will see that most altcoins got dumped in just a short period of time.
The other one is failing to predict the price, example is when a certain altcoins price is getting lower and lower so you sell it all to avoid losing money more, Sometimes the coins price might increase again.
Yep. Mostly because, of the hundreds(if not thousands) of altcoins created, the majority was just for pump and dump and only a select few have managed to stay. Not to mention all the fakes/scams.
Another risk is that when trading altcoins, one would have to be constantly monitoring the market as it's a very volatile one.
As for speculating with bitcoin, it may not be as risky as altcoin trading but is still very stressful.

Yes stressful if you are a day trader, but if you are into a long term investment with bitcoin I think you won't have any headache. With regards to altcoin trading, you need to be clever. You can participate with pump and dump coins, or ICO scam coin. Just make sure you exit when a profit is seen. Don't be greedy and be happy with the possible profit you will have when you exit. Stay longer holding the coins and you will be bagholding worthless shitcoin.