Intel
Thermal heat problem

I m a student in pune and i m using intel processor since 2 years and it was ok... but from past 20 days i m facing the problem of thermal heat.

Whenever i switch on my pc after 10 to 15 mins it gets restarted,

and after that it displays the message.."restarted due to thermal heat problem".

then again when i restart after sometimes then again it works properly n after 15 min the same problem arises.

i have kept my pc in the same room temperature since 2 years.

please solve my this problem.

please reply soon.