I have had a few calves do that through the years but not in several years now. They would walk along like the were in pain then just flop down and lay out and kick. They never died and would get alright. I started to think they were constipated and started giving them human laxative pills and would give them 2-3 at one time once only. It seemed to help them and they would be fine in a day or so. I don't know if this helped or they were going to work out of it anyway but that is what I did.