I believe what you're describing is an adrenal surge, one of the symptoms that happens at perimenopause due to hormonal fluctuations. It's a panicky feeling that's not caused by any outside stressors. I have it too and I hate it :(
If you have pressure in your chest that radiates, along with the feeling that your heart is "beating extra hard," you should proceed to the ER out of an abundance of caution.
I don't know what it is, but I have it too. I usually notice it most when I'm first waking up from sleep. It starts in my chest and works upwards. Feels like pressure in my chest and like my body is being suffused with... something. It goes through my arms -- makes them tingle a bit -- sometimes makes my legs tingle a bit too. Definitely feels like it fills my whole head and face. It feels like my heart beats extra hard while this is happening. But I'm not hot. I have hot flashes too sometimes, so these feel like two separate things. It's really been scaring me because I know some tumors (endocrine tumors) produce hormones. My brother had lung cancer and the way they found out was hormone surges were coming from the tumor and making his heart rate speed up.