Pedal doesn't rotate freely; occasionally comes with grinding / clicking Apologies if that has been asked before; the search function shows up related but ultimately different issues. Here's what's going on:

As I pedal along, occasionally the left pedal will be reluctant to turn nicely so as to stay horizontal and nicely level with my foot.

At the very least it will make a protesting clicking sound. Occasionally it will just completely refuse to rotate, which awkwardly bounces my foot.

So I got off the bike to see what happens. If I try to manually turn just the pedal on the crank arm, it's not a constant resistance. Rather, it'll turn a bit, then offer a big resistance that I can violently push past, producing another crunchy click grind sound.

Would anybody know what's going on here? Time to replace the pedal? Or just some tender love and care?

EDIT: Details of bike. Commuter bike. Officially 10 years old but pretty much everything got overhauled in the last 5 years, with a complete cassette / bottom bracket replacement last year.
27 speed (3x9), not sure what derailleur style would be. The one that most normal commuter bikes have, I guess? Hub isn't geared.
The pedal bearings are failing in some way. This may range from a ball or race physically broken to a simple lack of grease.

Depending on what kind of pedals you have you may be able to service or replace the bearings. The video linked at the end of this answer shows what's required to do so. It's possible but somewhat of a pain. You have to have the correct tools, if you have to replace balls you have to figure out what size they are etc etc.

If you have simple flat pedals the easiest option is to simple replace them as this type of pedal is inexpensive and easy to get hold of. Pretty much any bike shop should be able to sell you a pair and install them.