I’m not a professional, but this reminds me a lot of how I feel after eating insoluble fiber/how I used to feel after eating anything when my gut was more compromised than it is now.
Tbh, 16:8 is not that different from how many people naturally eat occasionally without trying - there may have been times before you consciously starter IF when you ate on that schedule just by chance. It’s highly unlikely this is what’s causing your bloating.
You don’t mention any problems with the fasting part of it…and it doesn’t sound like breaking your fast is what’s causing the bloating either. I would be interested to know what you are generally eating throughout the day.
There are lots of people who achieve desires results just by changing their eating window or watching calories. But plenty of other people end up uncovering that they have food intolerances or other situations that require further care or restriction. Paying more attention to how you feel after certain foods is a natural consequence of limiting your eating time. And also, giving your stomach a periodic break from digesting is also going to change stuff.