Why do I sprint in Fortnite when I just press w without shift?

So, I press w and I sprint without pressing the shift key. But when I press it, I suddenly run slowly. When I let go quickly. What shoud that? And how can I fix it?

In the game settings, you probably have Sprint to toggle and not hold, put it on hold then it should work.

Where exactly can I change that?

So I don't find that in the game settings.

Check out the controls

The setting is called "Standard Sprinting". You will find the gear ⚙️ symbol above.