This just happened to me for the first time the other day! I'm at a different gym (in sunny Savannah, GA) and instead of my normal lifting routine warming up with bodyweight lifts and stuff, I did 10 minutes on a rowing machine to warm up. I think my heart rate was higher than usual during the workout. And afterwards my ears wouldn't stop blocking. I was trying to feel what was happening, and it definitely felt like my eustachian tubes were constricted, which I guess could be because of blood pressure in my head. No amount of yawning or moving my jaw sideways to unblock them lasted for very long. And yeah, eventually it faded.
Man, it felt weird, though.