Where do we get the Belief that only Authorized Personel can Perform Baptisms??

Two levels of Priesthood.

"11If therefore perfection were by the Levitical priesthood, (for under it the people received the law,) what further need was there that another priest should rise after the order of Melchisedec, and not be called after the order of Aaron?
12For the priesthood being changed, there is made of necessity a change also of the law.
13For he of whom these things are spoken pertaineth to another tribe, of which no man gave attendance at the altar.
14For it is evident that our Lord sprang out of Juda; of which tribe Moses spake nothing concerning priesthood.
15And it is yet far more evident: for that after the similitude of Melchisedec there ariseth another priest,
...
21(For those priests were made without an oath; but this with an oath by him that said unto him, The Lord sware and will not repent, Thou art a priest for ever after the order of Melchisedec:)"
-- Hebrews 7:11-15,21

There are two Priesthoods, the Aaronic and the Melchizedek. The Law of Moses was under the Aaronic or 'lesser' Priesthood, while the New or Higher Law the Christ taught in the Sermon on the Mount is under the Melchizedek or 'Higher' Priesthood. See also Hebrews 5:4.

"1And it came to pass, that, while Apollos was at Corinth, Paul having passed through the upper coasts came to Ephesus: and finding certain disciples,
2He said unto them, Have ye received the Holy Ghost since ye believed? And they said unto him, We have not so much as heard whether there be any Holy Ghost.
3And he said unto them, Unto what then were ye baptized? And they said, Unto John’s baptism.
4Then said Paul, John verily baptized with the baptism of repentance, saying unto the people, that they should believe on him which should come after him, that is, on Christ Jesus.
5When they heard this, they were baptized in the name of the Lord Jesus.
6And when Paul had laid his hands upon them, the Holy Ghost came on them; and they spake with tongues, and prophesied."
-- Acts 19:1-6

Here Apollos had been baptizing without having the authority, and without giving the Gift of the Holy Ghost. When they learned that there was more to it, they were each Baptized again by the Proper Authority. This was done by Paul, who had that Priesthood Authority.

If Sacred ordinances are not performed by those to whom God has given the Priesthood, then those ordinances are not recognized by God.

Much like having a Drivers License, you might know how to drive, but without that License that gives you authority to drive you will get a ticket for 'driving without a License'. God works the same way.