Stay safe the same way you've been doing it for the past 9 months:
- Stay home and only jump through time when you really need to.
- When you do time travel, try to keep your distance from other people.
- If you cannot keep your distance, adjust your normal behavior and wear protective gear that minimizes the number of words that enter your brain from the brain of somebody else.
These are all preventative measures and not curative measures because, like COVID, there is no cure for a memetic infection. Yes your memory of specific events will fade over time, but general principles will worm their way into your worldview: they will affect the way that you process every new piece of information that you receive for the rest of your life. You can try to avoid talking to your friends about the moments you visited on your travels, but it's not that simple: the foreign memes have altered your subconscious, and you can't filter that.
... who am I kidding you have a time machine. You know how to wipe memories from a human brain, right? For the sake of an interesting discussion, I will assume that you cannot. Maybe the time travel secret is easier than we think. Maybe you didn't invent the time machine, maybe the time machine is a gift from your future great-great-great-granddaughter. Let's keep moving.
So how should you keep your distance? Six feet in this case is probably not enough. You really want to stay out of earshot, and out of visual range is even better. In fact, if the reason for your time travel allows you to pick a time when humans don't exist at all, that would be ideal. Modern corporations have dug up all the readily available uranium from the Earth's crust, so now they're sending equipment back in time to dig up uranium from the Precambrian? No risk of memetic infection at all, especially if the companies build walled-off campuses so that workers can't even admire the desolate pre-vegetation landscape and potentially get inspired with brave new thoughts about humanity's place in the universe. If you do need to pick a time when humans exist, though: try to stick to small towns or wilderness regions, only go out at night, and if it's cold in winter then make sure your destination is in the winter months so that the locals will stay huddled inside for warmth.
What if you can't keep your distance? What if you really want to visit Carlo Gatti's ice cream shop in 1853 London because you love the ice cream and there really is not, never has been, and never will be a good substitute? You need to stay on task: go in and get out as quick as you can, and above all talk to no-one except Carlo Gatti. Keep your eyes focused on your shoes or maybe a newspaper as you walk to his shop. If anyone tries to sell you something, shoo them away as rudely and aggressively as you can. Maybe dress like poor or sick person, so that people will leave you alone. Wear ear plugs, or use a wig or earmuffs to cover your ears. Wear thick eyeglasses even though you have 20/20 vision, since they will distort the light going into your eyes. When you get to Carlo's shop, don't stop to chit-chat: buy what you want and then leave. Find a nice isolated spot by the Thames to enjoy your ice cream... not too scenic though... and get back home as soon as you are done.
All of this of course assumes that you do in fact want to avoid a memetic infection. With no grandfather paradox to worry about, this seems like a rather strange desire. Maybe you live under an autocratic regime that regularly conducts psychological tests on its citizens to ensure that they remain loyal to the government, so it's dangerous for you and your friends to even think revolutionary thoughts? If that is the case, I'm not sure that you would want to risk your life for some ice cream in the first place.