"Motor coolant over temperature" warning turned on?

I experienced this issue twice (only twice I went on this long around 60 miles to and from and experienced it both the times).

I drove for around 35 miles (approx.) From my home and then I got a warning both the times saying, “motor coolant over temperature”. To be more specific, the first time I was a bit panicked and pulled off to the side and turned off my engine. But, only to turn it back on in a minute and see no such issue in that trip until reaching home which was 5 miles from there. However, the coolant levels seemed perfect for both normal coolant and radiator coolant (I see two coolant tanks under the hood). Later, I decided to take a look again if the problem persists, so I drove back 60 miles to and from home (been on multiple short drives in between and never had any issue). To see the same warning again after driving around 50 miles. This time, I was keen on observing the engine temperature on dashboard without panic and found the engine temperature to be perfectly normal (half the level as always). However, the other things I observed during this warning is my hybrid unplugged ev battery stopped charging as soon as the warning showed up and the car is limited to low acceleration. I pulled to the side and again not more than a minute I halted and started the engine back, there was no warning, and the engine temperature was the same (half level). I drove back home and halted the car and could see gradual decrease in the engine temperature reading which was normal too. For additional reference, I hear a humming sound at low speeds only when my gasoline engine is running. Could you please help me out addressing this issue? Thank you!