how long does it take for muscles to strengthen?

I'm not asking when muscles start to show. I lost a lot of muscle strength due to 0 exercise. Even my leg muscles are starting to weaken. And whenever I lift something heavy or something with some weight the next day my arms get shaky.. but I really want to become stronger again. If I started working out/exercising how long would it take for muscles to become stronger? And be shaky and become durable for me to keep building up muscle? Every time I start out something like push up it's hard for me to continue because of the shaking the next day and the pain.. and I feel like I'm getting nowhere :/