What you are describing sounds like vertical or horizontal rolling. Is your TV an older CRT picture tube type? Does this problem occur on all channels? Are there any nearby sources of electrical interference (such as electric motors, fans, etc.) that could be inducing the TV picture to scroll? Often times scrolling lines are the result of electromagnetic interference or poor/weak signal quality. There could also be unwanted interference signals on the AC power source. Another cause could be an internal component malfunction, or a component electrical misalignment due to deterioration or aging.
Check the rear of the TV. There should be a vertical scrolling rotary knob adjustment, and one for horizontal scrolling as well. They may be labeled simply "Vert" and "Horiz." Do not adjust the Vertical or Horizontal Size adjustments unless necessary.
If the lines are scrolling from left to right (or right to left) as you view the picture - that's vertical scrolling. If the lines are scrolling from top to bottom or from bottom to top - that's horizontal scrolling. If the lines are scrolling diagonally - then it's a combination of both vertical and horizontal scrolling.
Have someone watch the TV while you slowly adjust one control or the other (depending on which direction the lines are scrolling) and make one adjustment at a time to try to slow down or stop the scrolling.
If the adjustment knobs have no effect - then either the problem is not scrolling as I described above, or there is an internal problem with the TV picture circuitry. It would have to be professionally diagnosed and aligned or repaired as necessary.