Stuck Thermostat. The thermostat in your car is responsible for controlling the amount of coolant released into your engine. When your car first heats up, the thermostat closes and does not allow coolant into the engine until it is warmed up. The thermostat should open and allow coolant in once the engine is adequately heated. Sometimes the thermostat fails and remains closed. Might be something else. I know this cause two days ago the same thing happened with my VW Polo. Got the whole thermostat housing changed. Good Luck

Thumbs up to burping the system. Many modern cars need to have the engine purged of air after cooling system work. No idea why so many shops miss this. It creates an air pocket that stays there, and can result in fluctuating engine temps.

If it has been leaking, it might have air in the system and needs "burped". If not then question the thermostat.

When was the last time that the entire cooling system was drained, flushed and CLEANED to get the corrosion, rust and slime out?

may be a faulty temp. gauge or sensor.

be sure to check for any leaks.

Today my cars temp gauge went up close to the red as I accelerated then when I slowed down at a red light it went back to normal. I don't believe it's overheating. I got a brand new radiator recently but I did have a coolant leak a few days ago near the distributor which is already fixed. I checked today and the coolant level is fine. Its a 95 accord. What could this be?