Hedgehogs are nocturnal, so being awake only at night is normal. As for freezing when you check on her - how long have you had her? How much "cuddle" time does she get? How old is she? - it could be that she is just not used to you yet. Both my hedgies usually stop running on their wheels if I interrupt them - especially if I turn a light on.
As for the heat - hedgehogs MUST have a constant temperature above 74 degrees. Its best to not let the temperature change more than a few degrees. By not have a heat source, such as a room heater or a CHE set up, you are putting your hog at risk for a hibernation attempt and there are serious consequences related to hibernation including death. Heat is one thing that should not be "messed" with when it comes to hedgehogs.