Judderbar already stated there is no synchro ..
Reverse gear is significantly different to the forward gears in most manual cars
If you are following the ritual of 'a pause' before selecting reverse
Then you probably have a clutch issue..
If its cable operated..play with the adjustment
If... like my later punto... its hydraulic and does this, decide if you want to Spend £50 in parts and 2 hours work..
Or just drive into spaces.. and select reverse before starting the engine