Once the opening scene is finished, there are things that can improve the pacing. I've been judging contests for years and often the opening scene becomes slow and tedious or this scene goes so fast the reader had a problem knowing what is happening to who and why, Here are some things to make sure are happening in the opening scenes.
An opening can drag when you've put in every thing you know about the character's past. This is back story and will slow the pace and irritate the reader. If you need a bit here, make it short and perhaps in a dialogue sentence, internal or externl/
Does the book start with a bang. I once read one that began with a heroine's frantic run from a villain. Exciting but I really had no idea why she ran or even who she was. The scenes that followed didn't hold up to that exciting opening.
Once a book I read started with a battle with bombs exploding, people screaming, buildings toppling but the characters weren't there and I had no idea why this scene was there. If you're going to start with this king of bang make sure there is a character for the reader to focus on.
Then there are the openings that introduce a cast of character, so many the reader can't decide which character to focus on. Trying to bring all these characters on the scene at once will confuse the reader and make them put the book aside.
So from the beginning of your story, pacing is important. Pacing is one of the things driving the book forward. Make sure not to bore, confuse or any of the other problems when opening your story.