engine running hot for no apparent reason

'05 Accord LX. 141k miles. no bad noises, smells, smoke, leaks, or anything apparent to the non car person's (me) eye. coolant was low so I put some more in there but it didn't fix the problem. it's where it's supposed to be; no tell tale signs of head gasket blow.

I have not let it overheat but it does get to about a quarter way to the H pretty quickly (~5 minutes of driving, I pulled over once i noticed and let it cool down), no codes on dash. A/C is a bit loud, not a bad sound, just loud if that may help. maybe that has something to do with it?? I've got no idea about cars, but I'm scared it's gonna be big. I just bought it.

I'm gonna take it to get it checked out just in case but thought I would ask here too.