The theory may sound strange as Rick is faced with life or death situations on a daily basis; But when you consider how controlling Rick is as a character, it’s obvious the only way he’s willing to die is on his own terms.
The Suicide Theory suggests rick is depressed and when left to his own devices, considers suicide. We saw this literally happen in Season 2 Episode 3 when Rick tries to fry his dome piece after going through a rough breakup with Unity. But the Suicide Theory goes deeper. There is a helmet we see on Rick’s work bench that could be a suicide device. The helmet first appears in Season 1 Episode 2 and has been on his work bench ever since.
On a behavioral level, Rick is constantly getting himself into dangerous situations. Between never wearing his seat belt, and being willing manipulate his molecules into a pickle, it’s no surprise he may not be completely mentally stable.