How can I play a new piece with both hands together without pausing?
You probably know the reason for the pausing: fluency. It’s just like speaking a language. You need to know what to say in order to speak fluently.
Piano playing is just the same. Many players, regardless of their skill level, tend to pause and stop with pieces in certain sections due to lack of fluency. Often, lack of fluency is due to lack of practice on that specific spot.