Why my laptop won't turn on most of the time?

Can be tons of reasons, here is some based on how common they are by my expiriance:

1. Bad battery that causes some electricity anomaly. Try turning it with charger only

2. Bad charger. Can be tested with simple multimeter.

3. Some motherboard malfunction. Fairly hard to test unless you have a spare one.

4. Broken power button/switch? Usually rare but it happens.