Posi temp valve has hot and cold water reversed.  When the water is turned on, hot water comes out first.  As the handle is turned further counter clockwise, it becomes colder until only cold as handle is turned to maximum position.

Moen and all shower valve manufacturers follow american federal guidelines. Hold the unit in your hand with the handle facing you - the left side is the hot water inlet and the right side is the cold water inlet.

This is a very simple fix. NOTE: This is for a Posi-temp model only!! First turn off the house water. Relieve the water pressure at a nearby sink. Then remove the handle from the faucet. Remove the black plastic piece, then the two white plastic pieces (these control how hot the water gets by controlling how far the handle turns), then the metal cover over the center piece of the valve. Once these are out of the way, there is a small metal clip that you can see that holds the cartridge in place sitting in a **** on the top of the center piece. Remove this carefully with a small straight edge screwdriver, taking care not to lose it. Then with a small pair of pliers, pulling on the center of the cartridge, pull straight out. Once the cartridge is completely out, turn it counter clock wise, 180 degrees and then reverse the process. The hot/cold will be in proper location now.
Now for an older style, simply take the handle off, turn the center portion of the cartridge 180 degrees counter clock wise and return the handle. Hot/cold will now be in their proper locations.
Good luck.

do you have hot water elsewhere? if not, might be that your water heater is not heating.
if you do have hot water elsewhere, did you let the faucet run for a minute or 2.
did you have hot water before? is this a new house? new valve?
need a little more detail.
on posi temp valves, if there were no water coming out of the hot side of the valve, the valve will not operate.

If this is a Moen posi temp valve you may need to adjust the temperature limit stop. It is located under the handle. Usualy a plastic peice with grooves in it so it fits in another peice in the valve. If I remember right you pull this peice out and turn it counter clockwise to get more hot water. Do this in small increments and reassemble and test. I hope this helps.

spool valve is clogged remove clean replace

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

there is a clip holding the cartridge in place. You need to remove that and then there is a little plastic throw away tool that comes with a new cartridge that you use to break the seals loose on the old cartridge....then you use a pair of channel locks to grab the stem and pull it out. The new cartridge should come with detailed instructions.
If it is a moentrol valve...the part number is 1225 and if it is a posi-temp it is a 1222. Moentrol you pull out to turn on and then left and right for temp adjustment. Posi-temp just turns to turn on and you turn from cold to hot to adjust through the temp range.

turn the water off to the shower,sometimes you must shut down the whole house at the main ,near the water meter,then take the handle off slide the clip in front up and out then pull posi-temp straight out.replace posi-temp in reverse order.be mindful of the H/C indicator on posi-temp this will ensure you have hot and cold on right sides,if reversed just flip posi-temp.

Did this unit come with water stops built into the faucet body? Some of the newer faucets have stops built in and they need to be turned on. Also if you aren't going to plumb the hot in, you will need to cap it off but it should run without it unless it has some sort of balance in it. I don't think so though.

You do not mention what make faucet we are talking about.

Moen makes two styles of Shower valves
The one that you discribe is called a Posi-Temp the goes from off to cold and to hot as you turn the valve counter clockwise.
The pressure should be greater mid range ans the cold and hot water mix but generally not noticeable.

A Moentrol valve is that should have been iinstalled in order to have greater control on temp and pressure.
Moentrols work but turning the valve clockwise for cole and counter clockwise for hot and pulling out on the valve for the water to come on.
sanray