there is this common misconception that when a dog wags their tail, it always means they're happy or they want to play

which is only half of the truth

dogs wags their tails when they're excited or nervous so, just like cats purr to calm themselves down, it can be a sign of uneasiness

when you're not sure what a dog is trying to communicate, watch the ears because their language is less ambiguous

when they're tilted back, it usually points to fear, insecurity, confusion, aggression or some other kind of discomfort

wagging tail + ears tilted back usually mean "I'm not sure about this, chief"