The answer to 'shower slow draining' is that a slow-draining shower is usually caused by a clogged drain. This can be due to a buildup of hair, soap scum, or other debris in the drain pipe. Symptoms include water taking longer to drain and the shower filling up during use.
The first step is to try clearing the drain yourself using a plunger or drain snake. If that doesn't work, the clog may be deeper in the pipe and you may need to disassemble the drain or use a chemical drain cleaner. If the clog persists, it's best to call a professional plumber to inspect the drain line and properly clear the blockage.