Some heat is normal under heavy load. Excessive heat is a warning sign.
Stop using the tool immediately. Let it cool down. The cause is likely overloading. You are pressing too hard or using the wrong speed for the material. This damages the drill bit and strains the motor.
If the battery itself is hot, it's more serious. Operating time that has become excessively shorter can signal a battery problem, risking overheating, burns, or explosion. Do not use a hot or damaged battery.
Heads up: Never charge a hot battery cartridge. Let it cool first. Do not store the tool and battery in locations where the temperature may reach or exceed 50°C (122°F).