Returning to workouts

[JumDawg]

I use to workout when was younger around 3-5x a week never got "big" think i got close to 68kg at around 180cm tall extremely lean my body doesnt know what fat is.

I am now returning to it all after 8 years and i am wondering how i should try hit my workouts without going to hard.

I can constantly push myself to do more so ive been taking 2-3 rest days inbetween. During day of workout im fine, next day or 2 can barely move what i worked on. This never happened when was young.

Is it just age? Do i have to take things slower? Or do i just need little time to rebuild stablising muscles and tendon strength again?