I don’t know whether I understand your description correctly. If the problem
is that the table starts close to the bottom of the first page so that only
the header appears on that page, do this:
Select the header row, then select Format > Paragraph > Line and Page Breaks
tab and turn on "Keep with next". This will force the row to always be on the
same page as the text that follows. It is always a good idea turn on this
option for header rows.