Toilets, Sinks, Showers, Tubs and Disposals - Cold water pressure in shower inconsistent

Hi everyone,

I'm a total novice at this stuff but I'll attempt to describe what's happening. In the shower, when I turn the cold water knob a quarter turn, the water begins to flow, then it slowly weakens until there is no water flow. Then I have to give it a little more turn and then it flows. Here's the big problem, after I adjust the knob the second time, if I wait about 5 minutes, the water pressure will suddenly increase.

This makes it really frustrating when taking a shower because I have the water set nice and warm and then all of a sudden, the water temperature because ice cold.

I've replaced the entire faucet (is that the word) section of the shower in hopes of fixing the problem. I've read there's a possibility that I may have a blockage in the water line that is going toward the shower, especially since the problem doesn't exist anywhere else in the house.

Oh, the pipes. I think they're galvanized steel. I'm trying to remember while sitting at my desk at work. The house was built in 1976 and I live in Utah where there's major hard water. Hope I've provided enough information.

So, how can a novice troubleshoot this and attempt to fix the problem?

Thanks in advance.

Should I have posted this in the Plumbing section of the forum? Moderator - can you move this question?

Thanks