It's due to gas, acidity, gastritis only.
Lot of reasons for acidity whether you are not consumed acidity related food. Irregular food habit,
liver may not active properly, gall bladder condition.
Advice
USG WHOLE ABDOMEN.
Till than,
Light diet and plenty of water n liquid.
No fried fast and junk food.
Tab nexpro Rd 40 one in empty stomach for five days.
Tab meftal spas DS two times a day after food or sos.