Which herbal medications treat palpitations and anxiety?

Hi doctor,

I am a young adult female college student with anxiety and trouble sleeping, unsure of what anxiety is related to. I have a very sensitive nervous system (and just everything is sensitive in general in my body), and it could be related to that. I do not feel extremely stressed at the moment, and I feel like I am managing it well. I have been taking Magnesium 200 mg every night for a few months and I noticed I have been feeling so much calmer these past few months, and I have been able to sleep so deeply. But about one month ago, I developed heart palpitations that occurred mostly when I lay down for sleep (during positional changes), occasionally when just at rest. I suspected it was because of the Magnesium and got blood tests done. The levels were extremely high, but sort of on edge, and my body is extremely sensitive. All electrolyte levels were normal. I stopped taking Magnesium about three days ago, and heart palpitations decreased significantly (almost completely eliminated), and my heart rate felt much more stable. But I noticed anxiety or an overactive nervous system returning and took Magnisum again, and palpitations returned. Can you suggest some herbal supplements for this? I cannot tolerate other medications because of the side effects. Which do you think would be most effective for my specific issue? Kindly help.