How to get/stay motivated?

I work all day and am not home til about 7pm. When I get home I’m usually tired so I will “nap”, then maybe eat or clean up a little and shower then spend a little time with my SO before we go to sleep. I don’t eat a lot, I think my main problem is lack of exercise. How do I get myself motivated when I’m so tired when I get home?

Also: going to a wedding in less than 3 weeks any tips on how to look good fast? I know there’s no quick fix but any tips can help!