Flow restrictors are a small piece in the shower head that prevents some water from getting through. They decrease water consumption, but can also create a dribbly, weak flow.
To see if you have a flow restrictor, unscrew your shower head and look inside. Most modern shower heads have a small plastic piece where the head screws into the hose.
Most flow restrictors require some elbow grease to remove. In a TikTok, user @ez_home used a screwdriver and a pair of pliers to pop out the middle piece.
After you're done, screw the shower head back on and test it out. If all goes according to plan, you should notice a significant increase in your water pressure.