I have a few varieties that do that. Every pepper cultivar has its own growth habits, although each species has its own set of general characteristics to gauge even early on what species it is. That being said, however, there are always "boundary" cultivars that may be in a certain species, but have just a bit more genes for another species than others. Yours looks like a Capsicum Annuum species to me, but what variety, however, it's hard to tell at this stage.
I have a wild variety, from the species Capsicum Eximium (C01225), that does what your plant is doing the whole time it's been growing. It will grow about a centimeter before it starts to put out the next set of leaves. I also have a Capsicum Chinense (Tasmanian Red #1) that also does that between each set of leaves. In addition, I have a Capsicum Annuum (Elephant's Trunk) that had really long cotyledons and really long leaf stems. The seedling looks healthy to me, so keep up the good work!
I'm guessing by your post that you don't know the variety. If you didn't have the ID of the seeds beforehand, you may have to wait until the plant starts producing pods in a few months. Good luck, and I hope it turns out to be a great plant!