I think you have three approaches to dealing with this anxiety, and they are already discussed above:
- rationalise to reduce the fear, by looking at how you feel acceleration and how you do not not feel constant movement, and by looking at how the movement is not harmful.
- check for underlying physical and medical causes - are you doing this? Have you spoke to a doctor about this?
- reduce the fear by looking at the anxiety and addressing it directly. Where did this fear originate? Can it be addressed through therapy or through densensitisation? Can you talk to a therapist who deals with anxiety about this?