2004 Nissan Micra Crunching Gears/ juddering Engine

Don't know if the 2 problems are related- or if I'm just having terribly bad luck!

A couple of days ago, my engine started juddering, not massively, but certainly noticeable. It stopped the next day, and I put it down to water (we'd had a lot of rain). When driving, it was perfectly fine

It has started again today, and is much more considerable. I was driving a couple of hundred miles, and the gears began to crunch. Now it feels like whenever I stop the engine will pack out. When the engine is off I can work through gears fine.

Are these 2 related?

Many thanks in advance for any response

Katherine.