How can I start my Lenovo laptop start normally again?

What's the issue?

You should take the computer to a local computer repair store if you don't know how to fix it

Take it to a technician

With no clues what model Lenovo, what operating system, what happened just before (update, hardware damage, new programs used), what messages you see when attempting, warranty status, no blind guesses.
Search Google or find a repair shop.

If it won't start, something is wrong, and you need to take it to a repair shop.