Kohler shower valve (hot/cold switched)

If I understand correctly, you have single handled shower faucet.
Normally there is a wait for hot water to arrive at faucet.
But now hot water is already at shower faucet.

Single handled faucets have a mixing area inside valve where hot and cold come together before going into sink.
This mixing valve can have crossover where the hot and cold can pass through to each other even when faucet handle is off. When single handle faucets get old, this can happen.
How it happens:
For example another faucet is turned on inside house, and pressure differential between hot and cold causes hot water at shower handle to pass through mixing area and into cold water line.
So if another faucet has been run, then that lets hot flow to faulty single handled shower faucet.
To confirm this is the problem: turn on other faucet and put ear against shower faucet to listen for moving water.
This condition may also signal there is a water leak.
The problem is not harmful, but will draw cold water into water heater each time, and is energy wasteful.
Replace faucet or have plumber repair problem.

Replace valve canister- no construction- just remove after taking time to shut off water- a few screws and the job takes 15 minutes. I take for granted you have good water hot/cold to the fixture. This fix will cure most temperature balance problems.
The single lever system is a EZ care system. Note the canister can malfunction faster when exposed to untreated hard water.

Can you remove handle , behind handle there should be a dial to move to increase hot or cold supply.

Remember where you start and remove it and replace a 1/8 to 1/4 turn counter clockwise, just put handle on try it and see if it changes and adjust accordingly.

adjust ur anti scold the setting is set to low when single handle shower units are shipped they are set in cold mode for safety ur install/instructional paperwork explains such and also advises on how to adjust---remove handle and on shaft will see a blue and red plastic clips that are adjustable slide towards u and move red for more hot water test water continue till comfort level is reached for hot water

You have to remove cartridge and rotate 180 degrees then re-install. Was it removed or replace lately?

Your control handle is off by 180°. Remove the handle and turn the cartridge 1/2 turn.

1. If it is old enough, it is time to replace the control cartridge.

2. Check your supply stops under the counter, check that they are both supplying full pressure.

4yrs isn't very long, but I do believe the mixer needs a new cartridge in it. unless you have a loose knob/handle.But I don't thnk so. The temps should change almost immediatley. Have someone change the cartridge. It may need a special tool. If you think you can, do it yourself, the tool comes with full instructions. Make sure it does, consult with the pkumbing person .

Is this a dual handle or single handle? if it is a single handle
turn the valve 180 degree. if not, then check the cold water supply line.

This is a pressure balancing valve that needs both cold and hot water pressure to operated. It is an anti-scald safety operation.

Good Luck, Phil