1999 Pontiac Grand Prix Runs Rough/Chugs Occasionally, Possible Belt Noises

Hi guys -- okay, so we double checked the serpentine belt and it seems fine, changed the air filter because why not, and this is still happening. I do want to mention that I think I was wrong about it not chugging/surging when in drive, because it did this morning. When I started it up it was running rough in park, then reverse, but then in drive as well, so I pulled back into the driveway and put it in park and at that point it started running smoothly. There's no Check Engine light unfortunately.

Okay sorry if this is a duplicate reply, I keep trying to add info and nothing shows up, but when I re-try then both replies show up, and I can't seem to delete just one. I'm sorry, I don't mean to be spamming this question. ** Wanted to update and mention that we checked the serpentine belt and it seems fine, we also changed the air filter because it was time, and no change so far. The weird thing is that this chugging/running rough thing only happens when it first starts up. It does still happen in drive though, but at some point when we change gears it will stop. This morning for example it ran rough on startup, in reverse, in drive, and then when I pulled it back into the driveway and put it in park, THEN it started running fine. No Check Engine light, unfortunately.