@sktpfnr
Since you're saying you easily lose motivation, here's some advice:
1) Start the book chapter by chapter only if youre confident you can make regular updates, preferably if you have a proper timetable (dont make the same mistakes i make T_T)
2) If you have a problem of easily getting demotivated, then write the entire book at once and then you can choose to either publish it all at once or you can make a timetable for the days you update.
3) From (2) The second option would be better, because that makes readers anticipate the next chapter and gather more reads.
4) starting books can seem very exciting, but then again, there are people expecting from you and that can cause pressure, so make sure you're able to balance writing time and you daily life routine.