My coolant temperature going up and down?

My coolant temperature was raising high last night when i got off work but when i drove it this morning i didn't have any problems. I just brought this car last week it's a 05 Honda Civic DX

So did you bother to check the level in the radiator before asking this? If it rose one time last night but then fell back and was fine, could be a sticking thermostat. At worse, a head gasket issue. This is a hard problem to solve when we can't look at the car.

Verify if the temp raises while the car stands still and drops when it's moving. That means the cooling fans are not working. Usually the cause is a bad fan relay- $15 plug n play part. In the morning you probably used the climate control- heat/ac and the fan relay associated with that also ran the radiator fans so you didn't see the problem then. To be thorough, check the coolant level in the radiator while the car is still cold, to make sure somebody didn't fry the engine and blow a head gasket.