This can be the result of a few things. Most commonly, it is due to a partially plugged cooling system due to corrosion. With that, I would start by flushing and refilling the cooling system.
Here is a link that explains the flush and refill procedure:
If the system is clean already, the next thing to check is if there is an issue with a bad head gasket. If you look at the link below, it describes what to check for when suspecting a bad cylinder head gasket.
Let me know if this helps or if you have other questions.
Sunday, September 5th, 2021 AT 10:03 PM