Irregular Heart Rate After Doctor's Appointment

Has anyone experienced this or something similar? I have been traveling to a doctors appointment, I got out at a rest stop (I haven’t been able to take my beta blockers due to my testing) it’s about 105 temp. where we stopped I got half way to the bathroom and could already feel my heart pounding. When I got back in my car I measured it and I was at 160 it started coming down then went up to 180 i put water on my face in front of my ac to help regulate my temp it took abojt a total of 45 minutes for it to completely come down to a normal hr in the 80s. Does it usually take you guys a while to get your heart regulated? I ended up taking my beta blocker as well