An Azure Automation Runbook will work well for this. It only takes a minute to set up, however, if you've never used it before and are thus unfamiliar, figure more like 10-15 minutes to slowly walk through each step. Basic steps to set it up below.
Create Automation Account (you can skip this if you already have one):
Give it resource group and name and accept defaults for the rest.
Assign Role to Managed Identity
Navigate to your Function App -- Access control (IAM) blade. Click Add role assignment, select Website Contributor, Next, click Select members, type the first several characters of your automation account name until you see it in the list, click on it, click Select button, Next, click Review + assign.
In your automation account -- Process Automation -- Runbooks blade, click Create a runbook. Give it a Name, Runbook type: PowerShell, Runtime version: 5.1, click Create. In the editor pane on right, paste in code similar to below sample (don't forget to update with your resource group and functionapp names):
Restart-AzFunctionApp -ResourceGroupName MyResourceGroupName -Name MyFunctionAppName -Force
Click Publish. Alternatively you may click Test pane, run a test, close the test pane, then Publish.
Click Resources -- Schedules blade. Click Add a schedule, Link a schedule to your runbook, Add a schedule. Give it a Name, set the time you want it to run each day, click Recurring, change the dropdown to Day, click Create. If you don't want it to restart once every day then modify to suite your needs.
Please review pricing for Azure Automation. In your case you should fall within the free included units since the restarts shouldn't take up much run time.
Please click Accept Answer if the above was useful. If something is unclear please add a comment below.