Hello I watch a few 737 NG cockpit videos and the pilots go through their flows very quickly surely they do not use a checklist can any real pilots confirm, are they taught to memorize these checks in the initial training

They memorize the flows and memory items(for example, engine fire),Back up with the checklist.

Normal checklists are read after the flows are completed to ensure everything is set correctly. It would be unsafe to rely on memory for normal checklists as they are intended to verify that the flows have been carried out correctly. In cockpit videos you will invariably see the crew carrying out the flows without prompting from a manual and then reading the checklist from the QRH. Non-normal checklists are read as the procedure is carried out. However in some cases the first few steps of the procedure are memory items to avoid delay in carrying them out. The memory items, if any, of a non-normal checklist precede a dashed line in the manual which runs across the page. For example in the QRH, page 8.1, APU FIRE, the first two steps are memory items. Kevin Hall

so they would remember all those items from cold and dark to awake, thats goodi see thanks