Impreza 2.0r 2006 Rough betweven gears, and won't go into gear while running
 

Hey guys,
First of all this is my first time posting on a forum. Usually I can find answers from other people's problems but this time I couldn't quite see the symptoms
Basically, I noticed one day that when I started the car I heard a grinding and immediately turned the car off, turned it on again and it did not do it and car drove normally.
Then one day in a car park, I started car in neutral and won't go into gear, none of the gears including reverse. Tried pumping clutch and nothing would happen.
Clutch feels different but can't describe it.
20 mins later I start car again and it goes into gear as if nothing happened and drive off.
I took it to local mechanic and he couldn't see anything other then the diff oil smelt bad so he replaced that to see if that was the problem but it has since returned.
Lately I have noticed a little resistance changing gears, but other times it shifts fine.
It is a Suby impreza 06 2.0r (the dohc one)
Planning to take it in to another mech but I wanted to see what you guys think first.
Thanks to anyone who read this far!