More than likely a blockage, leak, or bad installation.
If some other showers, toilets, and sinks are having problems with running water then it's likely a problem with the entire water system, usually bad parts or a leak.
Diagnosis ....
If water pressure is good everywhere else, and the recent pressure seems to have changed, probably cleaning your shower head filters.
If never had good pressure but do everywhere else, you may need a lees restrictive head or shower valve, or your piping may be corroded.
Pressure is not the same as volume.... Most people say pressure when they want volume. You can have the same pressure to take a shower that comes out of a squirt gun, or one that comes out of a fire hose... The difference is the volume of water that makes the biggest difference. The answers above are mostly volume related.
Several factors could be causing the lack of hot water pressure in your shower. These may include a clogged showerhead, a faulty water heater, a blockage in the pipes, or a problem with the pressure regulator. It is recommended to check these components to identify and address the issue.
you have trash in your line take the shower head off and remove trash or possibly in water valve at shower
Maybe pressure balancer going bad or you don't have a pressure balanced valve
Hot water is spraying out into the atmosphere at high pressure. This causes condensation.
Well, if you take a shower with hot water, it should get worse, since a hotter temperature increases blood pressure....
There could be several reasons for low hot water pressure in the shower, such as a clogged showerhead, a faulty hot water valve, a blockage in the hot water pipe, or an issue with the water heater. Check these components to determine the source of the problem and address it accordingly.
This is probably a pressure imbalance problem or you have air in the lines. see the related video link provided.
A stuck or worn balancing spool in a pressure balanced valve.
My first thought is a leaky hot water line.
Run a new cold supply line from the source. This will drain less pressure from the the cold shower line.
The hot water in the shower does not last long because the water heater has a limited capacity to heat and store hot water, which can be quickly used up when taking a shower.
To increase the water pressure of your shower head, you can try cleaning the shower head to remove any mineral deposits that may be blocking the flow of water. You can also check the water supply valves to ensure they are fully open. Additionally, consider installing a high-pressure shower head or a water pressure booster pump to improve the water pressure in your shower.