Do all donkeys freak out?

Where I recently moved there is livestock... chickens, rabbits, and one goat and one donkey. I haven't been around donkeys so i don't know if this is normal or not but i was hoping someone who is familiar with them could answer me. He freaks out every few hours, his eyes bulge and he makes this really loud whining sound and shakes, it seems he's very uncomfortable when he does this. His owner seems to treat him really well, she lets him out to wander around the property freely when he's not inside his enclosed area, which by the way is really large so i doubt that would have an effect on anything. He does this throughout the day and into the night... they almost seem like panic attacks, donkey style. This doesn't bug me at all in the sense that it is annoying, not the least bit. What bugs me is if he's in pain. I don't know why but it makes me feel really sorry for him... so I am hoping someone will say that this is normal behavior so that I can have peace of mind. If you do say this is abnormal and that he's likely suffering... well i don't know if i can do anything about it but I'd still like to know. Thank You!