Racing heart in the morning only?

I'm 7 months pregnant and for the past 2 weeks or so my heart has been racing in the mornings only. So much that I have to sit down and take frequent rest periods until it passes. I don't feel dizzy or like I'm going to pass out, just extreme fatigue. I sleep fine, no major swelling or other issues going on. My resting heart rate is around 120 at this time. The rest of the day it's around 90. My ob booked an appointment with a cardiologist, and I'm waiting for bloodwork to come back, but I just wanted to hear if anyone else has a similar experience?