Depending on the take-off clearance issued by ATC.
If you accept an immediate take-off clearance it means you must line up and take-off immediately without stopping (ICAO).
If issued by a normal take-off clearance it is really your call, provided the AIP doesn't state otherwise. Some, normally busier airports have added departure procedures to be followed when a take-off clearance is issued, which could state that you must start your take-off role within a certain time, e.g. 20 seconds, to reduce runway occupancy time.
If you are unsure then ask ATC before lining up.
Hope this helps.