What should I do if I can't seem to be motivated?
Do you know this for a fact?  Are you always unmotivated?
I make up my mind to do something but I don't do it.
It's bad to be lazy, but it sounds like you want to do things, but just can't get going.  See if you can get a friend to encourage you at certain points.
It's just fine to be unmotivated, it's my right to be that way.
Being unmotivated will stop you from achieving your goals in life. You should find a source of motivations, something to help you want to do the things that you desire to do.