manual transmission problem

Next time it does this, try to see if it will go into reverse (obviously not in traffic). If it grinds trying to go into reverse, you have a clutch problem.

Consider changing to synthetic fluid, like something from Redline. I recently solved a problem with a balky second gear synchronizer with a change to synthetic. Well, okay, I got rid of the symptom, anyway. With over 150,000 miles on the car, the mechanic was pretty sure the previous owner(s) didn't ever change the fluid. Has yours ever been changed?

So you -have- tried reverse when it was balky about going into first? If it's smooth going into reverse when it won't go into first, it's not the clutch causeing the problem, it's an internal gearbox issue. The reason I asked about reverse is it is -not- sycronized like the forward gears are and it -will- grind where the forward gears won't, they just are balky about going in if the clutch is dragging.

Worn synchronizer......... :(

MY guess is that your "synchro-cones" (which some people might call "synchronisers") are getting worn out. The ones for 1st gear wear the most,

2nd gear 2nd-most, 3rd gear third-most etc,.....usually......depending on driving style and conditions

If the problem is just an occasional minor annoyance, then live with it

However it is possible that the "selectors" are worn and not working properly.

This would likely be hard to fix and also require removing and re-building the gearbox

However, first, look around/ underneath and see if anything is physically blocking the gear change mechanism from doing its job

Perhaps a piece of tree-branch, or a dead squirrel or rat etc has got jammed in there !

I remember once an old car I had with a floor mounted headlight "dip-switch" and my lights wouldn't dip

I thought I'd have to replace or re-wire the switch

It turned out that carpet had just gotten bunched up underneath it and jammed it !

Sorry I can't be more help.

cheers