studies have shown lifting heavy weights 2-4 times a week improves cognitive function (yer brain) and overall health and longevity (besides libido and sleep) a crap ton. starting strength is a great place to start on your own. or join and get a personal trainer. seriously, just do it.
let's face it, you need muscle
WALKING- seriously, it's so good for your health and your brain. walking can change everything, your creativity, your stress levels, all of it.
Couch to 5k is my favorite running program. Group fitness classes used to be my favorite, but now I enjoy solitude a lot more than I used to, but it's still a great option. The app gives you your cues over your music which is AMAZING! we used to have to carry around little pieces of paper to remember how much to run and when (that made me feel old)
just do it
if you don't want to do any spiritual hippie hippie stuff, just start with yoga. we are disconnected from our bodies and our feelings (which is why we are all miserable) and yoga connects you to both.
my favorite is YOGA with Adrienne on youtube. She is gentle and kind and her DEDICATE series is perfect for newbies.