The German name of this game Patt-schach literally means Stalemate Chess: the players start the game in a position in which they are both stalemated. Erich Bartel writes in Issue 5 of Variant Chess, winter 1991, that he played the games about 30 years earlier.
The game starts in the following position:
Each player may make with his first move any illegal move, except he may not take a piece of the opponent or give mate. (Note that he must make an illegal move, as no legal moves are available.) I.e., he moves any piece to an arbitrary empty square where it doesn't give check to the opponent. (Black may not make an illegal move that would put his king in check, e.g., after 1. Qe8-d3, Kd1-d4 is still forbidden.)
Pawns may only promote to a piece that is taken by the opponent. When no such piece is available, it is forbidden to move the pawn to the last row.
All other rules are as in orthodox chess.
A very short game which illustrates a clear danger to avoid is one played by Dr A. von Wilpert (inventor of Wolf chess), and Erich Bartel in 1960: 1. Nh8-c5 ??, Nh1-e5!. White resigned, as he cannot avoid being mated by black with Ne5-c6.
A related game is Upside-Down Chess.