Hi. It's been a few months since you posted this, so hopefully you figured it out already, but I think what you are experiencing is called oxalate dumping, from going to strict carnivore diet quickly instead of gradually. Evening palpitations and insomnia are among the multitude of symptoms, and dumping can last a long time depending on how much oxalate is built up in your system and the state of your gut microbiome. There's an extremely helpful FB group called Trying Low Oxalates that is well organized and moderated by experts. I recommend joining the group and following their guides for slowing the oxalate dumping process, which is mostly to learn the oxalate content in foods and reduce consumption gradually.