So just an update (perhaps someone can learn something).
Talked with the doc about the symptoms of what was happening, when it happened, my current diet and exercise and so on. She felt, as others have said, it could be my body trying to cool off since it seemed to happen on really muggy and hot days while wearing a backpack. However since I had something similar years ago she didn't want to brush it off so she had an EKG done last night. She didn't hear anything with her stethoscope but there was something that the EKG picked up that she wasn't sure what to interpret it as but will talk to the cardiologist when they come in next week. I had my heart measured and such via an ultrasound years ago when this first happened so she didn't think that was necessary again since nothing was found.
My resting heart rate was 54 beats, which she found odd but not alarming. But I have always been sub 60 when resting since I started riding so I am not worried.
For right now she recommended taking it easy when it is hot out, said I might need to increase my salt intake since I drink so much water, and I am getting blood drawn later this week to get a basic metabolic assessment (or something to that effect). Also I need to keep an eye on when/if it happens again and try to make some notes on what was happening, how I felt, how long it lasted and so on.