Fall while crawling?

My baby has been crawling for a while now. She's showing interested in walking and standing, but still crawls everywhere on her own. Recently I've noticed while she's crawling she'll take 5 or 6 crawls then fall flat on her belly with arms and legs spread out to the sides. At first I thought she was wanted to crawl faster than she could and maybe she was tripping, but I don't think that's the case. She isn't tripping on her arms and this happens both while she's going fast or slow. Has anyone ever seen this before? I'm trying to get a video of it but it happens randomly.