My car was doing the same thing earlier this year. Sometimes the engine would pause during cranking for what felt like a full second before it eventually turned over and popped off. My timing is set somewhere around 10° or 12° BTDC, but it's not high compression by any means.I noticed when the car was hot it had trouble turning over, the starter was struggling like the timing was too advanced. But my timing is set at 6 degrees before TDC, that shouldnt be a problem. Going to go for another drive tomorrow and see how the car starts when it has got nice and hot.