there could be a lot of reasons for engine heat up.
head gasket symptoms include, but not limited to, bubbles in the radiator on cold start , or milky residue seen on or near the radiator cap and engine oil cap.
however, before going for a big job like gasket, get your radiator serviced, check radiator cap, check for any hoses or pipes leakage.
my swift was also decreasing water and heated up once. got radiator serviced, changed the radiator cap, and Alhamdulillah car is working fine now, not reducing water, nor heating up.