TV comes on and works fine, after some time lines scroll.

Is it vertical roll? Or horizontal roll? It could be both.

This is caused by loss of vertical and/or horizontal synchronization of the scanning lines that produce the raster.

It is usually caused by a defect in the electronics section called the deflection circuitry.

You may be able to adjust it back enough to get it working if you can find the vertical or horizontal "hold" controls (they may be called by some other name). They are sometimes seen at the on-screen display section, sometimes on the front or back panel and sometimes inside the back cover. On newer sets it is factory fixed and their are no user adjustments. So, you might have to poke around until you find them.

If you cannot find them, or if you do find them and they don't adjust enough to lock in the picture then you will need servicing and the cost will be to replace the IC or transistor that produces the hold lock on the deflection system.

Hope this leads you the right direction.

Good Luck

If my solution proves useful please accept it.

Regards
Arjun

Check the power voltage .may be its an over voltage problem that is going in to the main board so due to that the component getting over heated and due to that this is happening.check out the pcb board voltages.this will clear the doubt.

It sounds your TV lose Video Sync signal during function and get video sync signal back when you give it rest.

Possible cause can be lose connection or dry solder joints in video signal section. It would be fine if you post / comment back with model and brand of TV.