MacBook air fan restarting after every 15 seconds. No screen seen.

My Macbook air behaving in strange manners

1. When started after taking gap of some days, boot sound can be heard but loading is way too slow. Bar below Apple icon takes forever. Sometimes screen is also seen and I can even log in and and operate normally. But then it freezes and needs force shutdown. For that whole day it wont start again.
2. When battery is very low (1-5%) it will boot. But as soon as battery percentage goes above, it freezes and needs force shut down
3. After it is force shut down, it won't start normally for several days. And when started fan will come to life and will again go off in around 15 seconds

Has anyone been through this? Please give your troubleshooting tips.