You are correct. There is no spike protein in the vaccine itself. However, by injecting cells with a synthetic mRNA that encodes a viral spike protein, the Covid mRNA vaccines directs human cells to MAKE a viral spike protein. So your own body becomes a sort of spike protein 'factory'. That process should evoke an immune response without a person ever having been exposed to the viral material itself. It may be that, as I said before, those who experience an adverse reaction, are particularly spike sensitive? The vaccine/spike may also induce an autoimmune response in some and perhaps the body continues to produce the spike protein? There is mounting evidence that vaccine-induced long Covid is real (search "Antibodies mimicking the virus may explain long haul COVID-19, rare vaccine side effects"). 13 months after being vaccinated I checked my antibodies. I had no Covid exposure (IgM - neg), but my antibodies were still high (SARS-Cov-2 IgG - 5347 AU/mL ( < 50 ) H). The immediate response to the vaccine I experienced within 15mins (tremors) was, as you say, probably not due to the spike itself (too soon), but more likely a reaction to the polyethylene glycol. The other cascade of long-covid-like symptoms followed within days.

Can you please clarify what the process is as far as spike protein. My understanding is the same as yours as far as the MRNA vaccine not containing the spike protein. However I thought that the MRNA tells your body to create the spike protein so that your immune system would then create antibodies for it and have them hanging around if you do get infected. It seems what you are saying is that the MRNA in fact instructs the body to create antibodies at first instance to the spike protein. Your response is appreciated in advance.