Too large space for input fields

I'm struggling with a form (in Bootstrap 4) which takes the whole (fixed) container width, there is nothing else displayed on the screen. It looks okay-ish on smaller screens, but on large ones it's ugly. What is the best practise in these situations?

I've tried:

• full width input fields, looks too large
• half width input fields aligned left, looks unintentional, like half of the screen didn't render properly
• half width input fields, two in a row, stacked next to each other, I think this is an anti-pattern
• half with input fields aligned center, looks amateur, unnatural

Any suggestion is appreciated!