I've made a small video of the problem.

https://youtu.be/PfopJPqEv0I

You can hear the popping noise 3 times:

1. Needle touches the record
2. Needle raises from the record
3. The motor turns off

Could it be a grounding issue between the turntable and preamplifier?

Or maybe these old capacitors that needs to be replaced inside the relay housing?

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Thanks,

Kim

If there was a grounding problem you would hear an annoying hum all the time.
The sound you are hearing is normal for an unmuted phono signal. I have a transcription turntable without any muting circuit and it does that same thing. 

I am not familiar with the workings of your particular Beogram but that does look like it could be a phono signal muting relay. 
Can you observe the relay assembly when the Beogram is turned on to see if there is any activity there?
It likely works off the lowering mechanism to unmute the signal so there may be a switch involved to operate the relay.
Does the service manual have an adjustment procedure for it?

-sonavor

That's the start(stop relay.
The muting switch is a passive sliding switch sitting near the tonearm base, operated by the lift/lower arm.
The tonearm wires and the output signal cable all go to the muting switch (unless your Beogram has the socket for an internal RIAA, in which case
the socket sits in between).

Martin

Ok, so it is not a grounding issue.

This is the back of the turntable and the tonearm base (I believe) with a red square:

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Could it be that the switch should be cleaned with contact cleaner? (how can I get to the it without breaking anything)

Should I care about the capacitors (I find it strange though, that there appears to be an electrolyte capacitor when the whole unit is driven by ac..) I have red that many capacitors are failing on old electronic gear.

Appart from this the turntable is working very well (appart from that it doesn't always want to lift and return the tonearm when the record is finished, but thats a minor problem I think).

Kim