John 8:44 states that the devil is "a liar, and the father of it" meaning the one who started all lying. Lies are things that are not true. Doubt would be that ground where we feel like we are wavering or considering two positions, one of which is true and one of which is false (a lie).
In 1 Kings 22:21-22, a spirit proposed to cause the downfall of Ahab by being a lying spirit in the mouth of his prophets. In Genesis, the serpent lied to Eve. So devils can lie to us directly or through other people.
You cannot be forced to believe a lie. But a lie may be presented to you in idea form or through other people. You may think about this lie and start to think, "what if this is true?"
Jesus met the postulates of the devil by using the word of God (Matthew 4). He did not ignore the questions, but He used the word of God to cut to the heart of the issues raised by the devil. So let's head in that direction.
You say that Jesus looks like just a man at the start of His life. The Bible calls Jesus both man (Matthew 25:31) and God (John 1:1). So if He is fully man and fully God, then we should expect Him to look like he was fully man. Especially at the beginning of His life. His ministry and revealing as the Christ did not start until after His baptism near age 30 (Luke 3:23). So we should expect Him to look like a normal human at first; Isaiah 53:2 states that "there is no beauty that we should desire him." He took on no human advantage, including good looks; there was nothing outwardly to distinguish him.
Now let's address the hoax idea. Hebrews 11:35-38 describes some of the things that people of faith have endured as a result of believing the Bible. Unbelievers do not dispute that the disciples were tortured and killed for their faith. Does it make sense that the disciples would all be willing to die for something they knew was not true? Would the leaders who did not believe bother to persecute them, if they could simply point to a dead body? If they stole the body, would not one of the disciples admit it to gain their life? What did they gain by creating this hoax? Severe persecution. Was the motive of the hoax to deceive or entertain? Would these people deceive Jesus' mother? If not, why would she be in on it? If your leader is dead, why not just go back to fishing, since that's how you made a living since before this all started?
If Christ is no more than a man, what is it about Him that drives unbelievers to use His name as a curse? What is so wrong about Him that makes men dead set against Him? Compare Christ with people's reactions against Him- who sounds more insane, Christ or those who rave against Him?
The reason I ask you to consider this is because faith is not what you believe about yourself; faith is what you believe about Christ. So look at the whole picture of Christ; who He was from beginning to end, what He did for people, and what He went through willingly, and what He said. When the Bible talks about the condition of the human heart, does it ring true in your life? How could a hoax pull that off? It even speaks the truth about the people who rail against it.
Doubts can come from ideas or experiences that challenge truths. From experience, knowing God's word and understanding His point of view more and more can help the idea-based doubts resolve themselves. Don't be afraid to examine an idea, and question the question!
For a circumstance-based doubt, it takes faith and patience to see the outworking of challenging circumstances and experiences (see Job).
Hope this helps.