In my experience, it’s most likely holding the bars incorrectly or putting too much weight on your hands due to either bike fit or core issues. But start with proper hand placement.
your hands should bear the most/all weight in the same places your hands would bear weight if you were doing a push-up. You should NOT be placing any weight in the webs or areas between your fingers. There are a lot of nerves there that can be irritated.
You should also not be bearing weight on the actual fingers by, say, hooking your hands over the hoods and bearing the weight on your thumbs.
Hopefully that makes sense. Once you hold the bars correctly you likely won’t even need any padding in your gloves.
Here’s an article that may help:
https://thedocandtheyogi.com/news/20...eruse-injuries