This is NOT normal. This is a design defect in Toshiba LCD TVs of certain sizes. Check the Toshiba website - the warranty has been extended to cover this problem.
Toshiba Tv Power's On For 3 Seconds Then Goes Off. What Could It Be?
I know what you're talking about. I have a Toshiba and it does the same thing. If it sits for a little without being turned on (like a few hours) it has to build up power. Mine turns on normal (for a few seconds), turns itself off, turns back on with sound but no picture, back off, then finally, on normal again. If yours does the same, don't worry, it's normal.
Try turning the remote away from it as soon as you turn it on or if you haven't already, turn it on with the on/off button on the TV. Could the on/off button on the remote be sticking?