I would be treating it as colic until the vet could get out there.
A bit of a story to tell: At a large facility I used to board at there was a very nice reining gelding who would constantly kick his stall and break the door in the evening, had been doing the same thing for close to 3 years, but would only do this after he ate. It was thought to be a behavior issue, nobody thought colic. They put a trip hobble on him (hobbled both fronts with a line to each rear so if he kicked out he'd pull his front feet out from under himself in a last ditch attempt to persuade him to quit destroying stalls. I hated that they did this, but he was destroying property and they are some of the most highly regarded horsemen in the state so I didn't question their methods) I was out there late at night, around 10 or 11 or so and heard thrashing, he was down, couldn't get up, and was full blown colicing. I untied his legs, got him up, started walking him out and called BM which called vet and owner. Normally I would never go into another boarders stall and tamper with their horse, but this poor horse was clearly in distress. Vet came out, oiled and banamine, no luck. Brought him to their facility where they performed emergency exploratory colic surgery, they discovered he had a large section of intestine that was knotted and some was starting to die, they removed something like 12ft. Where it was knotted loosely gas would build up and cause him pain, hence the kicking, and the vet guessed he had this knot for nearly 3 years and the hobbling just aggravated the issue that night since kicking out is what helped move the gas along, and he wasn't able to do so. Anyway, if I hadn't been there that night he would have died according to the vet. Apparently last check was done around 9pm and he looked fine and normal then.
I guess my moral here is to not rule out colic because he isn't showing classic signs, have your vet out to check him ASAP. If it turns out to be nothing, great, but if it is something, quick action may be the difference between life and death.