Hyperinflation can be also caused quite nicely by hiding normal
inflation by governmentally fixed prices and rationing,
as often happens during wars. This governmental act can lead to
a scenario where people can not spend all the money they
earn, because a) there are only few goods available (or even only
a fixed amount per person) and b) people can not pay more money for
those goods they really want because prices are fixed. The money,
which can't be spent, is saved, but this saved money
is (nearly) worthless, because no goods existed which could have been
bought with it. Therefore no consumption is relinquished which
could be invested to later produce goods
the saved money could be spent on.
If the conditions change later, i.e. the prices are freed, people
can spend all their money but there are (probably) still not much
more products to buy (remember no investment happened).
Inflation will very suddenly take care of the excess money. This
is mainly the reason for the hyperinflations in Eastern Europe
when regimes went from communistic (fixed prices and a
limited amount of products) to capitalistic (free prices but still
derelict industries).
In East Gemany the to be expected hyperinflation was avoided in 1990
by exchanging East-Mark 2:1 against West-Mark. This
ensured an overwhelming victory in the next election for Mr. Kohl but was IMHO also one of the reasons why the
eastern-german economy went from no. 1 within the COMECON to
nearly extinct within a few years: The loans of the
companies had to be exchanged 2:1 also and due to that
almost all of them were broke from the beginning. So hyperinflation
might sometimes be a good thing ;-).