Are you suggesting time travel or just you wake up in say 1995 as you at that age?
Do you get to choose how far back you go? Waking up in the middle ages at your current age wouldn't work well for a lot of people when the average life expectancy was much lower, and you wouldn't have access to modern medicine.
If you get to choose how far you go back, retain all your amassed knowledge and (for a bonus perk) are young, you get to relive your life.
It's literally priceless... people aren't thinking big enough, buying shares? Pfff
Start Facebook, start Amazon, start Tesla, or if you want to go further back start Microsoft or Apple. Hell start them all or at least invest heavily in the ones you don't want/have time to start.
Congratulations you are the wealthiest person on the planet, small countries look at your wealth with envy.
But are you happy?