“The best activity for health is one that is fun for you, so it’s easier to be motivated. For example, walking. The best time to go for a walk is whatever time of day you can do it consistently.
For many, that is first thing in the morning, because it is harder to come up with excuses and it is before “life interferes”. You may have to get up a little earlier.
To make it a habit: “Just do it” for the first few days, then hopefully you’ll start to enjoy it.”