I think it will help if you will narrow down your question into the type of game that you are looking for.
Personally, most relaxing android games would include Candy Crush, Piano Tiles, and Color Switch. Except Candy Crush, there's no limit into playing the two latter games I've mentioned. You can play them for as long as you like.
Now, if you want something more challenging, you might want to try 2048. It's a give that includes a series of addition when two tiles combine together to form a higher number until the sum reaches 2048. Quite an achievement once you made it. Another game, which may enhance your vocabulary is Wordscapes. It doesn't have a limit too. And this can be pretty addicting.
If you want a strategy or group type of game, I will recommend Mobile Legends. It may take you quite some time to get to know the game but once you do, you'll never spend a day without playing it.
Hope this helps. Let me know if you need more suggestions.