This morning I experienced an electrical power cut at home for the
fourth day running. The power outage only lasts about 5 minutes and
there are no obvious causes. The only ‘pattern' to the power cuts is
that they seem to take place a few minutes after switching off my
electric shower (note: a few minutes after, not immediately).

No fuses appear to blow, and the power is restored after about five
minutes. I've done no electrical work prior to this happening and
have been using the shower for approx four months without any
problems.

Any ideas?