It is condensation from the engine and should only last a couple of minutes. If it continues after warm up, you may have a blown head gasket or cracked block. Look for milky residue under the oil cap, and if you can, look into the oil cap opening or run your finger around the inside the filler hole and see if you remove any milky residue. DO NOT use any kind of engine block sealer or stop leak, you will be causing more problems than you want. Stop leaks have been known to clog up radiators, thermostats, and heater cores. restricting the flow of coolant
Check your oil and see if you see any while stuff on the stick or in the oil, before you start it up. That is from a cracked block. If so then get some K&W block seal, not the other cheap stuff, and use it before it gets worse.
In cold weather some water coming out is normal condensation. But if it continues after it is fully warmed up it must be coolant leaking into the engine from a head gasket or intake manifold gasket. Look at your engine oil dipstick for water mixed in with the oil. See if there is oil in the coolant.