avoid upload wait?

I am wondering, if there is a trick to make a board starting the sketch instantly instead of waiting for an upload.

Reason is: I want my battery driven device to start the sketch without delay.
(an upload new code only, if e.g. the reset button is double pressed)

specific device is an adafruit itsybitsy M0

I recall reading about it somewhere. The reason for the couple seconds of pause before the sketch runs is due to the boot loader waiting for commands for flashing a new code. You may want to do some research but it should be possible to set to run immediately but It may disable reprogramming without resetting fuses in the future.

Some boards immediately start the loaded sketch immediately at power on; e.g. the Leonardo.

You can program your sketch via ICSP using a programmer; that will wipe the boot loader and your loaded sketch will immediately run.

You might want to ask in one of Adafruit's forums, the bootloader on their itsybitsy M0 is considerably different from the optiboot used on most arduinos, so I'm not sure what would be involved. On most arduinos, when you first power on the board it automatically skips over the delay in the bootloader and goes immediately to the sketch, and you can completely eliminate the bootloader by loading the sketch using an ISP programmer.

Thanks. I askes the adafruit guys.
It is possible, but requires a bootloader code change and reflashing the boatloader:

I asked them, if that wouldn't be a idea for a general change of the bootloader:
defaukt: intsnat on
double tab the reset button. sketch upload