Do pilots have to stop at the hold position of the takeoff runway?
No, there is no mandatory stop. Typical clearances given before departure are:

BigAir 123, hold short of runway 36.
BigAir 123, line up and wait runway 36.

Former phraseology in the US was &quot;position and hold&quot;.

BigAir 123, behind landing A320, line up and wait runway 36, behind.

Note the word &quot;behind&quot; being repeated at the end of the clearance.
The interesting ones:

BigAir 123, are you ready for immediate departure?

It will be asked by the tower controller to assess if they can squeeze BigAir 123's departure between two landings, for example.

BigAir 123, cleared for takeoff runway 36.

It can be given to an aircraft still on the taxiway. In such case, BigAir 123, who will have proceeded through checklists and briefings while taxiing, will turn into the runway and takeoff, without having to stop at any point.
It is possible that the crew actually needs to stop, to finish their preparations. In such case, they will normally report not ready for departure, if asked. The tower controller doesn't want aircraft making unexpected stops on the runway, especially in a single-runway airport, this can result in the following landing having to go-around.
Also note that the word &quot;takeoff&quot; is used only in the context of an actual takeoff clearance or its cancellation. Otherwise the word &quot;departure&quot; is used, e.g., are you ready for departure? Also see the Tenerife disaster.