OPSWAT Gears for Android is a free app which quickly delivers a report on your device security and health.
There's absolutely nothing to do, at least initially: just launch Gears and wait as the app scans various system areas: is Android up-to-date, are you using a lock screen, is your storage encrypted, are you opted-in for ad tracking, and - maybe most usefully - are any of your current network connections accessing a known malicious website?
Within a few seconds Gears displays a security score based on these factors. If it's anything less than 100/ 100 then tapping the score displays a breakdown showing the areas where there's an issue, and tapping any of those explains step-by-step what you can do about it (open this, select that, disable something else etc).
A "Device Health" section runs a few basic performance checks - free RAM, battery life, hardware speed, last reboot time - before displaying a health score, again with explanations of any issues and what you can do about them.
Selecting "Pro Mode" in Settings gives you more details on your security status. In particular there's a list of all your current network connectiona, including the remote IP address, location and connection status (you can also view these on a map).
You can also link the device to your Gears account, allowing you to view and manage its status remotely. This costs nothing for up to 25 devices - Android, Windows, Macs, Linux - and there are subscriptions available if you need more.