So rattle likes to make the most noise in mornings when it's been shut off all night. By daytime when everything is nice and heated up, can barely hear it, more like figment of my imagination.

Anyone think it might just be the clutch? How easy are those to replace?

theoretically, i would think its OK to be louder on a cold start, there is oil in the compressor that starts to cycle around.... mine is just loud in general tho haha

I wouldnt worry bout anything til it starts failing. When mine failed, first it sounded like rocks were jumbling around inside it and then eventually the pulley just froze, partially melting the belt (just cut the belt off if that happens)