If needed I can post the full sequence but this sounds like a flame sensor issue.
Sometimes the flame sensor gets dirty and does not heat up fast enough, cleaning it makes it work better.
option 2 is burner. the orifice can be dirty and need cleaning (Reduces gas flow and thus heat) or the air/fuel mix can be off a bit.
In my case.. it was the control board, but in yours, I think not.
Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times