I've been using the same whey protein for over a year now.

Lately, I notice more and more that I sometimes get a general feeling of malaise when I consume a whey protein shake -- but only when I haven't done a workout. This feeling sometimes lasts an hour or two. But the weird thing is, when I consume a whey protein shake after a hard activity like a weightlifting session or running I have no issues.

I have zero issues with consuming other dairy products like yoghurt or cheese.

Could this be an intolerance? I plan on trying vegan whey next but I still have 5kg left so I'm curious if others have experience with this as it doesn't seem to align with the typical whey intolerance symptoms.