I have a Database with a Table that have 198,000 records with people names and ohter information ?

I need to retrieve a field from this table:

I'm using the next sintax:

SELECT * FROM DATABASENAME!TABLENAME WHERE TABLENAME.FIELDNAME;
LIKE "%NAME TO FIND%"

OK, THIS WORK THE "NAME TO FIND" RETURNS BUT:

THE RECORDS RETURN VERY LOW:

1ST run of the instruction: 29.220 sec (ok Good Time)
2nd run of the instruction: 145.93 sec (What Happen)
3rd run of the instruction: 120.26 sec (???)
4th run of the instruction: 124.20 sec (???)
5th run of the instruction: less than 2.000 sec (Excelent)
6th run of the instruction: less than 2.000 sec (Excelent)

How could I speed the 4th first searchs ??

Thanks and sorry for my english.