Water expands and pressure increases when it is heated.
Connections are only hand tightened during production. Usually that is tight enough.....but sometimes not enough. Just tighten the connection (and check all the others under sinks, in any compartments etc.)
If water is dripping from the Pressure Relief Valve (PRV) in the water heater outside access compartment.......then you need to establish the 'air gap'
Turn water supply off
Open closest faucet (Hot side) to relieve line pressure
Open PRV via lever........when water stops running out let it snap close (caution water could be hot)
Turn on water supply
Close faucet