@markalyce
Besides the manufacturer and numerous researchers this is what Mayo clinic has to say about it.

Seroquel is a powerful antipsychotic medication used for conditions like schizophrenia and bipolar disorder.
While it has a sedative effect, drowsiness is considered a side effect, not the primary intended purpose when used for sleep.
Experts are actively discouraging off-label use of Seroquel for insomnia.
Insufficient evidence exists to support its safety and effectiveness for insomnia in the general population.
Serious side effects are associated with Seroquel, including weight gain, increased blood pressure and cholesterol, and a higher risk of cardiovascular events.
Alternative treatments are available for insomnia, including other medications and lifestyle changes.
However, in some specific cases:
Seroquel may be helpful for sleep problems related to symptoms of schizophrenia or bipolar disorder.
It might also help reduce anxiety and depression, which can interfere with sleep.
Its use for insomnia should be confined primarily to patients with comorbid mood or schizophrenia spectrum disorders.
Important considerations:
Even at low doses, Seroquel carries risks, notes GoodRx.
Discuss any sleep issues with your doctor to determine the most appropriate treatment for you.
Your doctor will weigh the potential benefits against the risks before recommending Seroquel for sleep.
In summary, while Seroquel can cause drowsiness, the Mayo Clinic emphasizes that it is not recommended as a sleep aid for primary insomnia due to insufficient evidence of effectiveness and the potential for serious side effects.

Here's what the Cleveland clinic has to say about it.

Seroquel is a powerful antipsychotic medication used for conditions like schizophrenia and bipolar disorder.
While it has a sedative effect, drowsiness is considered a side effect, not the primary intended purpose when used for sleep.
Experts are actively discouraging off-label use of Seroquel for insomnia.
Insufficient evidence exists to support its safety and effectiveness for insomnia in the general population.
Serious side effects are associated with Seroquel, including weight gain, increased blood pressure and cholesterol, and a higher risk of cardiovascular events.
Alternative treatments are available for insomnia, including other medications and lifestyle changes.
However, in some specific cases:
Seroquel may be helpful for sleep problems related to symptoms of schizophrenia or bipolar disorder.
It might also help reduce anxiety and depression, which can interfere with sleep.
Its use for insomnia should be confined primarily to patients with comorbid mood or schizophrenia spectrum disorders.
Important considerations:
Even at low doses, Seroquel carries risks, notes GoodRx.
Discuss any sleep issues with your doctor to determine the most appropriate treatment for you.
Your doctor will weigh the potential benefits against the risks before recommending Seroquel for sleep.
In summary, while Seroquel can cause drowsiness, the Mayo Clinic emphasizes that it is not recommended as a sleep aid for primary insomnia due to insufficient evidence of effectiveness and the potential for serious side effects.

I have a friend who took Seroquel and developed Seroquel induced diabetes.
Take care,
Jake