I would argue there is never really a bad time to invest. Over the long-term, making consistent, routine purchases of equities/etfs has proven to be one of the best wealth generation strategies in history.
That said, during times like this, you have to be comfortable with purchases being highly volatile over the short-term. You could buy today and be 20% lower in the next 6 months. Or, you could be 30% higher. You really don't know, and it is amplified even more in this situation as the United States is making some of the largest policy changes ever when it comes to global trade, and seems to change their mind in an afternoon.
Take a long-term approach to your portfolio, and today is as good as any to buy. Just don't fret over whether or not you've made the right decision over the next 6 months, year, even couple years. Because it could be rocky.