This is normal!
And most times I convince myself to just do it, and you know what? I have never regretted doing my workout. I generally finish feeling refreshed and energized. The more I exercise and am consistent with it, the more I enjoy it.
Exercise is crucial to keeping your body functioning properly and to keeping you strong to avoid injury. Many people focus on how many calories they are burning or even worse "earning a treat" because they worked out. You don't earn dessert. You eat dessert because you make a conscious decision to eat it, not because you worked out. Exercise is not a punishment to get good reward.
The reward is your health.
When you bring your health as the main focus for your WHY, it changes your perspective. You exercise because you want to feel your best and because you want to care for your body. When you eat and exercise to achieve health, all of those other things (like weight loss, etc) come along naturally.
Below are all of my posts on fitness. I also have a page specifically devoted to Running if that is your interest.