Weird thing keeps happening?

Hi, I dont know where else to post this question because I am fairly new to this app and still playing around with it and figuring it out, but..does anyone ever get tired out of the blue? I was just standing in my room and then all of a sudden I started feeling hot and nauseas and my heart started pounding. I’ve noticed it happening for the last 4 days and I have to sit down in order to rest. It’s the weirdest thing because my heart will pound like I just got done running but I’ll literally just be standing somewhere. I am also 140 pounds and 5’4, so it’s not like I’m super overweight. My body just feels tired at random times.