1988 Chevy Camaro 88 Camaro Overheating at idle/slow speeds

I have an 88 Camaro that drives great but the only thing is is that when I am driving at slow speeds below 45 mph or sitting at an idle it seems to heat up rather quickly. If I am driving around 55-65 it gets to about 240 degrees, but if I am driving highway speeds between 70-85 it never reaches above 220 degrees.

I have a few ideas of what could be wrong which are:
1. - Coolant flow problem, seems to me maybe there might be something affecting the flow of coolant.
2. - Need a new thermostat. But if I needed a whole new thermostat I imagine it would start overheating at any speed
3. - Could be a problem with the Radiator and/or radiator fan.

I should mention this usually happens when the engine warms up. If I first start driving at city speeds for the first ten minutes, the temp gauge will go up to 220 fairly fast but then it seems the coolant kicks in and drops the temperature down quite a bit, but after it does that one or two times it seems to start heating up faster and not start cooling down until I hit 55 or above.

Does anyone have any ideas?