theme issue then white screen

[Stephen Jenkin]

I think I may be having a similar issue. My problem comes and goes,
but what happens is that the theme doesn't seem to load (which means
loss of menu bar and links, side bar, as well as looks), and then if I
try to open a new page I get a white screen, which is then all I get
whichever page I try to open. Bizarrely, if I go into wp-admin and
view a different page from the page list, I can eventually get back to
normal, but this problem still comes back regularly.

Does anyone have experience of this? Can anyone help?

Thanks ever so much,
Stephen