Symptoms can be varied depending on severity/cause. Uncomfortable in stomach area .looking round, kicking up at the tummy, lying down , getting up or rolling.
Also sweating , not interested in food not passing droppings.
If you are in doubt at all get the vet it is not something to leave, a simple visit and some injections to ease the pain may be all that is needed, but the longer you wait the outcome can be serious , needing operating or worse.
my husband had a vague notion that my daughters horse may have something wrong because we have caught her laying down in the field a couple of times, just asleep but we hadn't seen her before x
Today my daughter was able to sit in field with her - it was lovely such a privilege for my daughter x