Search Indexer always Resetting & Restarting after reboot

Follow this method to resolve the issue:

First, change the value of this Registry key.

Open Registry and navigate to the following key: You need to change the value of key SetupCompletedSuccessfully to 1. Now close the Registry and rebuild the Search Index.

Manually rebuild the Search Index

To rebuild the Search Index, Open  Control Panel > Indexing Options and click Advanced. Next, on the Index Settings tab, click Rebuild > OK. Wait for a while as it may take some time. Read: Search Indexing has been temporarily paused

Change the Registry value again

Once the indexing is completed, reboot the computer and again open Registry Editor. Again navigate to the key path mentioned above and this time change the value of SetupCompletedSuccessfully back to 0. This should help! If it does not, then you may also Run the Search and Indexing troubleshooter and see if that helps. The troubleshooter checks for general problems with the Windows 10 search function and resolve them if possible. Thanks to Pete Feistmann for this solution. He was facing this issue and found that this method helped him resolve the issue.