I don't know if it applies to this machine, but a common method would be pressing and holding the power button for up to 20 seconds.
However, I suggest you try and start the machine without an aerial connected.
If this allows the machine to start enough for you to get into menus , then make the unit rescan without an aerial to clear out all channel placeholders - which may account for why the unit is hanging.
If you are able to do that, then it would be better to manually tune in stations - if the unit has such facilities - as an automatic scan may pick up too many transmitters which may be what is causing this whole issue.
( I have brought all posts on this issue into this thread)