02 bmw 3 series. One in ten times when you try to start car thier is no compression

It is impossible not to have compression sometimes. compression is the product of the pistons coming up with the valves closed. Either it is there or it is not, it can't alternate between the two as compression loss would mean the presence of a major permanent mechanical failure. Likely you have an intermittent spark loss or fuel is not entering the engine (or both). You will need to do testing to determine which condition you have, or have a competent shop do that diagnostic work for you..

Hav u used a compression tester on the vehicle-must read values to confirm--it may be other things that appear to be the problem-if there is a low reading then rings/valves/oilpress or heads are of concern