Water rolls downhill. An imperceptible slope in your floor will send water to the low side. Mop everything up, dry all the plumping connections and watch things. The first thing that will happen is a drip, which will make something wet. Then, the source will be easy to trace.

Thank you @Sigrid, confirmed - it is the water heater.

Trying to get through the night without having to mop every 30 mins. Turned off the incoming water valve to stop it from getting cold water. Will this stop the leak temporarily or no?

Frankly, the leak is likely to be in the tank. Turning off the intake valve will mean that the leak won't produce more water than the capacity of the tank. Most tanks have an overflow or emptying valve. If you think the leak will produce large volumes of water overnight, you can empty the tank via the overflow valve. The easiest way to do this is to use a garden hose and send the water to the nearest drain.

If turning of the incoming water stops the leak, you're good. Otherwise, having a close drain and/or a long hose is helpful.