"Acting goofy"???

Would appreciate your comments. Friday night I put the boys in as usual. Barley trotted into his stall, as usual and then just laid down as soon as he
got in. He was calm-no concerns at all. He got up about 2 minutes later and slowly ambled to his grain (which is minimal), took a bite or two and then
down he went. No thrashing, no kicking, no nervous looks at his flanks, no tail wringing...just down. He continued this behavior for about 10 minutes.
Called the vet and since he (horse) showed no signs of distress, Doc said maybe he is just "acting goofy" and for me to keep an eye on him and to call
if anything else happens. Nothing else happened-he was fine on Saturday. Go figure...