I've been in IT for 25 years and have been laid off 3 times. I anticipate being laid off a fourth time here due to "location strategy".
My first layoff was in 2009 after the company I worked for was purchased by private equity and they canceled our product.
My second layoff was at a law firm that wanted to exit my line of business.
My third layoff was in the early days of covid and the freak out was in high gear. I worked at a small startup which relied on relocation of people around the country - this stopped.
Minus the covid layoff, each one caught me by surprise. I was midstream in projects, had project plans and big recent successes. In one case I was conducting a morning scrum when the HR guy (grim reaper) rolled into my office with management to share the great news. There was a few days when I was stunned and a bit angry at my employer.
What you should do now : cut your personal expenses to the bone and save money. If you know or suspect a layoff, do it now. If for some reason you make it out the other side and still have your job (and want to stay), you will have some financial padding for when this happens again. Also, retool. Been putting off a certification? Perhaps research into a work related topic? Get on it. Been on the fence about a career change? Make a plan now, not when under duress. Considering starting a side gig? That's right! Do it now.
Take rosy messages from your manager with a grain of salt. It is in management's best interest to keep you in place and working until the last moment. All of my managers knew what was coming and they never shared it in advance. When layoffs were happening elsewhere, I was being gas-lit by my manager. They may have a short lead time, but they all knew in advance.
When you get laid off, give yourself a few days to breathe, relax and gain perspective. Some people get emotional. It is not the end of the world. You are going to be fine and no one is going to die. Unless you had issues with job performance you likely did fine and this was a financial decision. The money you saved NOW will give you some padding and time to find a job.
Finally, you may select a bad job out of desperation. I did this twice. Sweat shop dev jobs that paid poorly and worked you to death. Also, making a poor decision could set you up for the next layoff (which is probably why in 2 of my layoffs). My previous employers didn't pay severance - only accrued vacation required by law. I never want to work for places that treated people like that. If you have a financial pad you can be more discerning in your job selection. Also, exchange personal contact info with people you may want references from in the future or keep in touch with for networking. At this places, when it happens, you are disconnected immedately.