The next crisis will likely be a liquidity crisis which is being driven by a mix of massive debt bubbles everywhere. You can’t really say what the cause will be, as there is a big feedback loop.
Take consumer credit card debt. At present, it is at an all time high in the US at over $1 Trillion. Defaulting on credit card debt is also on the rise, with millennials driving the trend.

Most Americans have less than $2K in savings and rely on credit cards to make ends meet ay the end of the month. Increasing defaults puts banks in the red and forces them to curb lending. (Or at least it will have to at some point.) This causes a liquidity crisis as suddenly people have less cash available which impacts everything.
Millennials are the main driving force of the economy, as they make the most big purchases. Houses, cars, education, gadgets, etc. Start limiting their credit and they buyer fewer iphones, cars. etc, and this hits businesses who start finding it harder to make a profit,
In reality, it’s worse than just making a poor profit. A lot of businesses are in massive debt and can’t secure credit or investment capital when it is clear that their comsumer base is drying up. Businesses subsequently go bust, then you have unemployment hike up a notch and even more of a liquidity crisis as even less money starts flowing back into the economy.
All that, though, is just the repercussion of having too much consumer credit card debt. At present. there are debt bombs and other potential triggers everywhere. The big one is US national debt. This is only servicable as long as interest rates are low, due to the way the US and other governments take on more debt to pay the interest on debt which is already outstanding.
(Yes, it is that crazy.)
This puts governments in a Catch 22 situation when the next crisis does hit. They can lower interest rates to pay their debt and continue as normal. However, this obliterates the value of savings for regular people and spurs inflation. (The last thing you need when you already have a liquidty crisis).
At present, car sales and even second-hand car sales are down globally. This points to an already present consumer liquidity crisis. As this escalates, it will also hit the real estate market and then the dominos will start falling.
If not selling your home in 2019 means putting your house on the market in 2020, the sooner option is the best one. In a survey of 100 U.S. real estate experts and economists by real estate information company Zillow, released in May, almost half expect the next recession to occur in 2020.
Source
Then you have the debt exposure of banks to toxic derivatives debt, coupled with the fact banks can’t be bailed out by governments in the next financial crisis, as the money to that was all used up in 2008.
It’s all really a big mixed bag of awfulness with a timer ticking down to all out chaos.