Contacts
Hello, my contact list seems empty although when someone calls me his/ her personal details appear
You may try to restart your iPhone first and make sure you are running the latest software version.
It depends on where your contacts were stored and if there are any groups filtering applied.
To check the filters go to Contacts, press on Groups on the left upper corner. Make sure that they are all selected.
If you recently deleted a mail account or disabled contacts for any mail account, that may cause it as contacts might be saved to mail account. You should add or enable contact that mail account again. Either go to Settings > Passwords & Accounts > Add account or Enable contacts or Settings > Mail > Accounts > Add account or Enable contacts (steps to follow may differ depending on which software version are you running.
Let's say your contacts were saved to your iCloud account;
Go to iCloud settings > Enable Contacts
If your iCloud contacts were unintentionally deleted;
Go icloud.com > Sign in to your account > Account settings > Advanced settings > Scroll down and click on restore contacts.
Ps: You must have enough storage to restore any missing information
You may also see below articles they may help.
https://support.apple.com/en-us/HT205018