MK5 GOLF GEARBOX HELP!!

[LiamApex]

Hi, recently the temperature has been getting hotter round here, it has gone from 9 Degrees averagely to about 27 degrees: during this time when I am changing from 2nd to third or third to forth. My gearstick will feel like it has not engaged properly. Then when I release the clutch it will grind and I have to disengage and renegage the gear. This is happening more often recently, the gearstick also physically shakes in 3rd gear.

Any ideas??

Thanks,

Liam