This will sound like water isn't entering the bowl fast enough, but there's a twist...

When I flush it swirls a bit but doesn't go down. So I'll flush again and it will work a bit better. Then again and I'll get a good flush. Now it will work well as many times as I want to flush it.

Come back several hours later and it won't flush again.

It's almost like I have to fill the pipes with water before it will flush.

Any ideas? The tank is filling completely and it empties into the bowl quickly. The holes in the rim have no scale buildup. Pouring water into the bowl from a bucket works about as well as flushing. The first time it'll mostly change the water but it won't flush. Second time it'll pretty much flush. Third time it'll flush well.