Your GI tract is adjusting its activity to the new eating schedule. Your gut bacteria may also be adjusting — especially if you’ve changed what you eat as well as when you eat (e.g. eating much less sugar). Things should settle down within a week or so.
Make sure you’re drinking plenty of water and (in your eating period) eating plenty of vegetables for fiber, just to keep things moving properly.
Temporary GI weirdness seems to be a normal part of adjusting to IF. It happens to lots of people when they first start IF. It goes away relatively quickly as your system adjusts.