@seditthis A bit of tmi, but I've been experiencing similar while running and I've decided to chalk it up to gas pain. It always happens .5-.75 miles in, and if I pass gas, it helps.
@unmaskedhearts In the first tri, I tried to schedule my runs for when people were not cooking- avoiding early/mid-evening especially. I'd also just take a walking break if the nausea got too bad.