Central Europe here consists of three regions: The eastern part of the central European plain (Poland, the Slovak Republic and the Baltic Republics); Bohemia (the Czech Republic); and the Danube plain (Hungary and Romania). These regions are open to easy migration from the east, and are moderately accessible from Germany and Northern Europe. Even the mountain barriers to their south have not stopped all mass migrations. No surprise that if your ancestors came from here, their ancestors may have had far flung origins. Above all, Eastern Europe, Central Asia, and Mongolia are the major sources of nations migrating to this region.
At the beginning of the study period, the northern part of Central Europe was inhabited by the ancestors of the Baltic nations (Prussians, Lithuanians, Latvians) and of the Finns. The southern half housed people whose languages and histories have not been preserved. All of that changed during the Roman and early Medieval Periods. .
First - Third Century Germanic migrations: During the first century, several Germanic nations, the Goths (later to divide into Visigoths and Ostrogoths), Vandals, and Burgundians, migrated from what is now southern Sweden to what is now Poland. They didn't stay, but slowly filtered south, with the Vandals and Burgundians settling in what is now northern Yugoslavia, and the Goths heading for the Ukraine by the third century. Still, if your ancestors were in Poland in 500 CE, then their ancestors might also have lived in Sweden, in 1 CE.
Fourth Century Hunnish migrations: Invasions from Central Asia and Mongolia are a common theme in this region. The first historical one occurred during the fourth century when the Huns, a Central Asian-Mongolian people, invaded the Ukraine and the Danube plain, settling en masse in what is now Hungary. During the following century, they turned up in many places in Europe before assimilating, so they will have left a diffuse but distinct genetic mark. The closer your ancestors were to modern Hungary in 1000, the more likely that they had Hunnish ancestors in Central Asia in CE 1.
Fifth Century Slavic migrations: During the fifth century, the Slavs appear in history, having migrated into Eastern and Central Europe from their homeland in the Ukraine and Southern Russia. At this time, Slavic languages came to be spoken from the Baltic shores of Poland to the southern Balkans. Only Romania, which held onto its version of Latin, and Hungary, which adopted the language of its tenth century Magyar invaders, have non-Slavic tongues. So, if your ancestors were in any of these countries in CE 1000, they had ancestors in Southern Russia and Ukraine in CE 1.
Sixth century - the Avars, also of Mongolian/Central Eurasian origin, immigrated into central Europe and settled on the Danube plain in Hungary. They were subjugated by the Franks during the ninth century and ceased to exist as a nation (except in the south Russian region of Dagestan, where their language is still spoken). The closer your ancestors were to modern Hungary in 1000, the more likely that they had Avar ancestors in Central Asia and Mongolia in CE 500.They were followed by...
Tenth century Magyar invasions: During this century the Magyars completed a 900 year slow trek from their home in Western Siberia to the Danube plain of modern Hungary. Like the Huns, they intermarried with the peoples of southern Russia and the Ukraine among whom they lived, and extensively raided in Central Europe and Southern Germany before settling down. Their genes represent an amalgum of all of the nations they had encountered. The Magyars gave rise to the modern Hungarians. If you are of Hungarian extraction, you certainly have Western Siberian, Ukrainian, and Southern Russian forebears. Even if you are not from Hungary proper, if you have Central European blood and your skull is unusually short and wide, you probably have Hunnish, Avar, or Magyar genes.
Later Middle ages. Throughout the Middle Ages, German speakers slowly invaded and colonized countries to the east, eventually overwhelming Prussia and maintaining large minorities in the rest of Central Europe. If your ancestors were Christians with German surnames living in this region in 1490, their ancestors probably lived in western Germany in CE 1000. During the Renaissance, Austria became the nucleus of the cosmopolitan Hapsburg Empire (Later called Austria-Hungary) which included the modern Czech Republic, Slovakia, Slovenia, Hungary, Croatia, and bits of Italy. If your ancestors lived in this region in 1800 CE, their ancestors could have come from anywhere in this Empire in 1490 CE.
1795 CE. This is the year that Poland ceased to exist as a nation, being divided between German Prussia and Russia. If your ancestors were in Poland in 1800, it's possible that their background was German or Russian. Surnames and family folklore should help you sort this out.