Gps behaviour in the beginning of an training

Several times i don't get a good gps fix. When i am start with running i get sometimes a straight line and after a few minutes the gps line seems to be normal again.. I have the latest version with gps version 5.3. All seems to work normal except gps in the beginning. It's not every run but last weeks I see it more often happen. I have a Samsung galaxy s21 ultra which I use to sync my activities and get a fix.. do more people have the same problem or is this because of phone issues?