1999 Honda Accord Car get hot while Idle

I have a 99 Honda accord. It gets hot (well the temp needle goes up) while I am idle (in line at the drive through). It never goes all the way to hot and if I am idle in traffic or waiting at a light, it doesnt really happen, only when I am waiting in a drive through line. It doesnt run differently and it doesnt begin to smoke. As soon as I begin to drive, the temp needle goes back down to normal and my car runs fine. Is this something major (like my cooling fan not working) or something less major (sensor issue). I dont smell anything odd coming from my engine but I have not popped it yet either.

Thanks!