7mgte overheating problem

[87boosted]

I recently bought a 87 supra with the 7mgte. ive been driving the car for a little over a month with no problems. About a week ago it started running warm when its sitting. As long as the car is moving the temp stays normal but when you stop it starts climbing. Ive read a lot about the dreaded blown head gasket problem and I just wanted some advice before I try to replace it. I'm not sure if the head gasket is the problem, ive checked the oil and it doesn't look milky. I have also replaced the radiator and when I drained the old coolant it was pretty clean. was just wondering if it may be something other than the headgasket. Any advice would be greatly appreciated! thanks!