car overheats

[john]

The car has a new waterpump already installed about 30 miles ago, has plenty of coolant, a new thermostat as of yesterday and a slimline fan that is working. The car drives perfectly fine, but sometimes the temp guage randomly goes higher. It can be right in the middle, jump up to the higher mark on the guage and out of nowhere just fall back to normal. It doesn't get to the red on the guage, but it is close to it. The idiot lights turn on (battery, coolant) as it is hotter. I don't think another fan would really help as it was driven at 9:30 last night and it wasn't too hot. Coolant isn't leaking either and is full. Any ideas?