AFAIK they spawn on the top level of a pillager outpost all the time (not 100% sure). But is there maybe a single spot where he "respawns"? This doesn't seem to be tackled in any of the wikis.
1 Answer
According to Minecraft wiki:
Both regular pillagers and pillager captains can continuously spawn around the structure.
In Bedrock Edition, they spawn at or below a particular location in the outpost; specifically, they choose the northwest corner of the highest opaque block with a non-solid block on top.