SRS lamp and related phenomenon

Hello Volvo Forengemeinde, I have a problem with my Volvo V70I, built 01/2000, 2.4 Ltr 103 kw. When I start the car, the SRS lamp does not go out. In addition, and that I do the actual phenomenon, goes as long as the SRS lamp lights up, neither the Kpl. Tacho lighting, nor the blower and also not the radio. After the SRS lamp goes out (about a minute) the ventilation, speedometer lighting, radio goes without problems. During the ride this error does not occur. My free WHO kstatt has read out the error memory once. No error except that the passenger belt lock is listed. Now my question: Can all this have to do with each other in everything? If I think about it this way, the SRS error should always be present with a “defected belt lock”, ergo the lamp should be permanently luminous. What worries me is that the phenomenon of the missing speedometer lighting etc. is always present. What can this be? who, without any real errors in the memory, it becomes a big search. On the edge: The interior lighting no longer goes out when I start the engine or set it on ignition. It burns almost constantly. Can this be related somehow because both “mistakes” occurred at the same time? I hope one or the other has some kind of tip for me, what it could be, what I could check, what the workshop could check etc etc. I thank in advance for Your answers. Greetings Hendrik