I feel like my DS9 and DD6 are very self motivated and I'll mention some things that have helped them.We are very blessed to have gone to a montessorri Type pre school and K. The school works on developing one's inner self.

They constantly tell the kids it would feel good to do ...'
you look proud to have done that,
give yourself a pat on the back,

They don't get into the prizes or sticker - the prefer internal motivation. This is a process and takes time to develop. My kids current school is into the prizes that they seem to enjoy but I'm frequently reminding them that's nice but the best prize is the good feeling inside.