Awesome picture of my Honda getting towed away after it busted an axle.

Anywho, I seem to have a very strange problem with my cooling system, I have an assumption as to what it may be, but I wanted more opinions.

So, after my vehicle gets warmed up to operating temperature, while I am driving everything seems perfectly fine, but if I am doing stop and go traffic (unavoidable in NoVA), I notice that the temperature gauge seems to go up a bit, sometimes fast sometimes not so fast. I don't usually notice it at a stop light, but if it's stop and go traffic like, you stop, 2 seconds later go, then stop again, it seems to heat up pretty quickly, any ideas as to what it could be?

And some quick technical background, I had the temperature sensor in the engine changed a while ago, and one time I noticed it was pinging red, pulled over, the radiator was pretty dry, put a bunch of coolant in it, and drove home. It didn't ping red again, nor since then, I check it regularly, at least once a week, and I lose next to no coolant. No idea where that phantom leak was, or whatever it could have been, seems to have disappeared. Also, I do not know when the timing belt/water pump was replaced, my odo says 207xxx, but with the title when I bought it, it was at 204xxx and the title said 210xxx, so it may quite possibly be far above 207xxx.

Like I said I have an assumption, that it could be an air pocket in the cooling system, which while sucks, I do plan on flushing the radiator, because I have a new thermostat along with housing to put in, and was going to flush the radiator while I was at it. Is there anything else it could be? And for future reference, is there a way to bleed out the radiator for air, if I don't want to flush the system?