When I turn on the cold water it's piping hot for a few minutes then gradually turns, at most, to ambient temp, hot water is plentiful. Previous owner set up water heater like so: written on the cold water in line "Close in winter", when I did this it solved the problem as I had truly cold water, however, I run out of hot water within ten minutes in the shower. So I switched it back to the open position, (need those hot showers), but that brings me back to the never have cold water. Nuisance to say the least, all my clothes are shrinking that should be washed on cold! Thanks so much

There should be only one supply line going into you water heater. One cold in and one hot out, period. The person who sold you the house may have engineered (I am being kind) something that is total wrong. If you are not sure of how to replumb the lines please call a pro.
I have seen some retrofit installations where the cold water was hot for a few moments. This was due to cold supply line running down a long length of a hot air duct before it reached the faucet in question. The cold water sits in that pipe slowly heats up when no one is using water.

Thanks ballengerb1. The cold in is the only incoming line. It's really strange. It's piping hot initially and never really gets cold, and I seem to have endless amounts of hot water... hence the furnace diversion? But when I close it, the cold in line according to the "engineer" wintertime instructions, it's cold like it should be, however, I run out of hot water. I don't get it... I've run this by my plumber and he's had a look at it and was a bit perplexed as well. Nonetheless, he's coming to work on it next week and I thought Id try to get some pointers or tips. Thanks so much

A good plumber will unravel the engineered piping. You should not need to open an close valves on your hot water heater just because the seasons change.