WE just got a calf and her mother, at stock sale, yesterday. Calf does on nurse, not up often, and doesn't try to get up and get away when you come close. Lays around quite bit.
In my opinion, you have a sick calf. If you are lucky enough to have a vet that will grace you with his presence, call him/her out to have a look...and I'd make it sooner rather than later. In the meantime, give the calf a shot of Vit. A, E, and D and a shot of vitamin B. And if you have any antibiotic and banamine, give the calf that.