,Gear Shuffling Problem in Vauxhall Vectra 52 Registration

Some time I am not able to shift gear in between my driving. Say I am running on second gear and want to shift to 3rd gear. Then gear will be out of 2nd gear but will not move to 3rd gear, even if I try to move it back to 2nd gear, it got stuck.Can you suggest solution for this problem.
Many a times, if I stop the engine and try to shuffle the gear then it allow me to shuffle the gears.

My car has 83000 miles.
My car has a manual transmission.