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I can only assume that this is the form you are referring to. https://www.jotform.com/63005522694150
Although I'm seeing that the form doesn't have any conditions set up in it or widgets added in it, the form is long and fields are loaded at once when the form is accessed. Which is most likely the reason why the form loads slowly.
May I suggest you use Form Collapse instead of headers?
The Form Collapse can serve as headers dividing sections on your form.
Or, I think it would be better if you try using Page Breaks.