my tv goes off after every 5 minute?

Hello guys, this my first q in here
i've got this old tv and lately goes off after every 5 minute
i thought that some shaking would do the work,
but now it does not even go on anymore.
I would appreciate if u guys could help me, cuz i would like to fix this prob at my own, or at least learn how to do it.

p.s. the tv brand is Telefunken