Ok ladies. Is this normal:

I'm 12 weeks pregnant and since I've been pregnant I notice my heart rate randomly fluctuates when I'm doing absolutely nothing. Like right now, I've been laying down in bed over an hour and I noticed breathing harder and felt heart palpitations and my Fitbit said my heart rate was 101, it was 82 a few minutes ago. But this happens often. While sitting or laying down. It would spike just like that for no reason. It's this normal????